Previously known from the Finnish patent publication 98404 Bl is a method for continuous balancing of a flexible roller or cylinder, in which method the measured imbalance is compensated making new grooves or pockets in the roller or changing existing grooves or pockets. By balancing such a cylinder the grooves must be machined separately on the cylinder surface or there must be grooves before. For instance, in an uncovered paper machine tubular roller the surface is of metal and it is not allowed to make any grooves in it. On the other hand, making grooves in the inner surface of such a cylinder makes the construction weaker and the grooves also have an effect on the behaviour of such a cylinder by calendar nip contact. Making grooves on the roller inner surface is also a complicated and expensive stage.

By means of the method according to this invention the problems in connection with balancing of tubular rollers are solved and the quality and accuracy of balancing improved remarkably The method according to the invention is characterized in that the eccentricity of the centre of gravity of each wanted additional mass in the tubular roller cross section level, from the centre and the direction is determined measuring the circularity of the tubular roller of the corresponding cross section level and the deviations from it, additional mass needed by each wanted cross section level and its angle of direction is calculated, and fluid and hardening additional mass sprayed on the roller inner surface in order to compensate the eccentricity of the location of the centre of gravity in wanted tubular roller cross section levels.

Additional features or alternatives characteristic for the method according to this invention are presented in the enclosed dependent claims.

The advantage of the method is that the inner surface of the tubular roller must not be separately machined because of balancing. In the method the shape of the inner surface and the eccentricity error caused by it is has been taken notice of in the form the inner surface has. Necessary data to be measured from the tubular roller can in the advantageous embodiment of the invention be received by measuring from the tubular roller outside, whereat measuring is easily carried out. When the eccentricity values are measured along the whole roller length and registered at the roller cross section level, the track of the centre of gravity can be determined from roller end to end, which is the condition for continuous compensation of eccentricity. Compensation takes place by means of spraying mass simply on the roller inner surface without any grooves or pockets. The method does not cause any disturbance in the roller behaviour.

In the following the method is disclosed with reference to the enclosed drawing, where Fig. 1 shows the tubular roller from the side.

Fig. 2 shows the profile of form errors emphasized.

Fig. 3 shows cross-cuttings of figure 2.

Fig. 4 shows measuring of roller scatterings and dimensions.

Fig. 5 shows the tubular roller from the end with coordinates added.

Fig. 6 shows the tubular roller, which has eccentricity and additional mass, from the end.

Fig. 7 shows the tubular roller with a sprayed homogenous tape inside.

Fig. 8 shows the tubular roller into which additional mass is sprayed.

Fig. 9 shows the eccentricity value along the tubular length in x and y coordinates.

There is in figures 1-3 a tubular roller 1, which has, independent from different ways of manufacturing, always errors. There is in the tubular roller circularity errors and since it has an inner hole resulting in that the wall thickness also changes. These facts mean that the centre of gravity cannot be held in the centre, i. e. on the line of roller axis. Also the porosity of the roller material or other local density differences of material move the centre of gravity corresponding to the controlled cross section spot, off the line of axis.

In the method as per the invention the qualities of the tubular roller are measured from sequential cross sections chosen at wanted frequency. In figure 4 a measuring situation is presented, where measuring device 2 includes a measuring head indicating the circularity of the circle points of the outer circle of the tubular roller. Thus the measuring indicates scattering AR in the cross section in question. As sensor there is a precise untouchable distance gauge known per se.

Measuring sensor 3 measures the wall thickness by ultra sound principle, whereat an emulsion required by measuring is fed from nozzle 4 between measuring head and roller surface.

The roller is rotating during measuring and its angle positions and measured values corresponding to them are most suitably registered into a computer connected to measuring device 2. Measuring device 2 is moved in the roller direction, whereby at wanted frequency from the whole tubular roller a map of its form errors is achieved and it is possible to calculate the eccentricity value e and its angle of direction A per each chosen unit of length. The track of the roller centre of gravity, which is a continuous curve, is detected and by means of it, it is possible to determine the compensation mass coming to the roller opposite surface. By measuring it is possible to detect the volume of the tubular roller in the cross section, when to the cross section area also the lengthwise travel of the roller is always connected, may it then be a differentially short travel. When the density of such a differentially thick ring is assumed to be constant, the position and direction of the centre of gravity can be determined in the way described above.

Figure 5 shows eccentricity e in a spot and figure 6 shows the location of compensation mass 9 in the opposite surface of eccentricity e.

Figure 9 shows how the measured and calculated eccentricity e can be indicated in the x coordination and y coordination as function L of the length of the tubular roller. By means of these ones it is possible to determine into which angle position A + n the compensation mass in each position of roller length L shall be placed. The mass 9 size in each spot is determined by the size of eccentricity e.

Figure 8 shows spraying of compensation mass 9 on tubular roller inner face 1. The sprayer has a shaft 7 and a nozzle 8 in its top. Most suitably nozzle 8 is moved axially and the roller rotated in the way required by the angle positions. Roller 1 can also stay put, while the nozzle is turned and moved axially. Since the quantity of mass varies axially, can its size, e. g. the thickness of layer s coming to its surface can be determined by means of nozzle 8 transporting speed. Another alternative is to adjust within the time unit the quantity of mass 9 discharging from nozzle 8, for instance adjusting the nozzle opening or adjusting the nozzle pressure.

Most suitably compensation mass 9 is a hardening mass 9, which is fluid material sprayed through nozzle 8. Its hardening can take place independently, by means of heating or light, as by means of ultra violet light. Compensation mass 9 becomes homogenous tape, the thickness and/or width of which varies inside the tubular roller, and which moves from one roller end to the other on the inner surface along a track determined by the angel positions received by the measurements and the calculations.