The invention relates to a method according to the preamble of claim 1.

The invention also relates to a device according to the preamble of claim 5.

EP application publication 0 367 901 discloses a method and a device for measurement of web tension. The tension of a moving web is measured by placing close to the web a measurement bar having its outer surface curved in the running direction of the web. The measurement bar is provided with holes in which pressure measurement sensors are placed. An air cushion is formed between the moving web and the curved surface, the pressure in the air cushion being proportional to the tension of the web. The tension of the web is measured indirectly by measuring the pressure of the air cushion. The device suitable for use in the method comprises means for producing a reference pressure and the pressure measurement device is used for measuring the pressure difference between the reference pressure and the pressure of the air cushion.

One example of this type of prior art device is the measurement bar which is marketed by the applicant under the trademark IQ Tension and which is used, for example, in connection with the manufacture of a paper web for measuring the tension of the web, for example, placed in connection with winding after a spreader roll, and which is described, for example, in the magazine article Pekka Rinne :"ension profile is inhe7ited", PaperNews, vol. 14, no. 3, pp. 46-49.

An object of the invention is to create further applications for use in connection with said tension measurement bar.

With a view to achieving the above-noted objects as well as the ones which will come out later, the method according to the invention is mainly characterized by the disclosure in the characterizing part of claim 1.

The device according to the invention is in turn mainly characterized by the disclosure in the characterizing part of claim 5.

In accordance with the invention, additional functions are arranged in connection with the measurement bar, by which functions it is possible to replace other means and/or devices in connection with the manufacture of a web, in particular a paper or board web and other web-like products. Thus, other functions are combined with the measurement bar, so that, in addition to tension measurement and the control associated therewith, said device provides further functions. By disposing a dryer between measurement bars, or as integrated with a measurement bar or, for example, as a counter surface for the radiation of an infrared dryer, a drying effect is produced in addition to turning the direction of the web. In accordance with additional features of the invention, instead of infrared drying, an ultraviolet, microwave, radiation heating or induction heating dryer is used in this connection.

The invention provides savings in both investment and operation costs and, in addition, runnability and paper quality are improved. The equipment takes little space and is inexpensive in particular in machine rebuilds.

In accordance with one advantageous embodiment of the invention, a turning function is provided and a web drying device is disposed in connection with the measurement bar. The curved measurement surface of the measurement bar is formed so as to be at a desired turning angle, for example, 4-35°, preferably 10- 30°, in the running direction of the web. In this embodiment, the air pumped by the web, i. e. an air cushion, between the shaped measurement surface of the measurement bar and the web keeps the web apart from the device. Thus, by alternating a tension measurement bar having a desired curvature (all the units are

not necessarily coupled to tension measurement) with a dryer in the running direction of the web, the web can be turned and dried without a traditional turning device.

In accordance with one advantageous additional feature, for example, a profiling dryer is arranged in connection with the measurement bar, whereby it is possible to adjust the tension profile.

In the embodiment in accordance with one advantageous additional feature, an infrared dryer is connected to the measurement bar, by means of which it is possible to carry out, for example, the drying profiling of coating, which, when necessary, makes it possible to prevent the spreading need of the web and eliminate problems associated with web wrinkles in situations in which the "living"of the web is not even in the cross direction. The moisture profile can also be affected by means of the invention.

The moisture profile is affected such that after coating more water penetrates into the base paper at wet locations with the result that the web becomes slack at these locations. In that connection, more drying energy can be applied to these areas.

When the web is dried in the area where water has been bound into the fibres, i. e. at a solids content of over 60 %, the fibres contract in the cross direction (in the machine, the fibres are normally in the longitudinal direction) and tension increases when drying energy is increased.

In accordance with one advantageous feature of the invention, drying capacity is adjusted based on tension measurement in the cross direction such that higher drying capacity is directed at the areas of lower tension.

In the invention, in accordance with an advantageous embodiment, tension measurement is carried out by means of the measurement bar and the moisture

profile is corrected by means of drying. This embodiment of the invention is suitable for use, for example, in a press section and at the end of the machine.

In accordance with some advantageous embodiments of the invention, the measurement bar is used as a turning device in addition to tension measurement, and a drying effect, or a spreading effect or other suitable devices are combined therewith in an appropriate manner.

In the following, the invention will be described in greater detail with reference to the figure in the accompanying drawing, to the details of which the invention is, however, not by any means meant to be strictly confined.

In the embodiment of the invention illustrated in the figure, a web W is conducted from an unwind station 31 past a measurement station 33 to a coating station. An arrangement in accordance with the invention is placed before and after the coating station 30 of the web W, which arrangement comprises a tension measurement bar 20 with a dryer 22 arranged in connection therewith, the dryer 22 being followed by dryers 23,24 whose counter radiators 25,26,27 are located on the opposite side of the web, and after a guide roll 35 there is a winding device 40 for the web. The measurement bar 20 turns the running direction of the web W in a contactless manner by means of an air cushion formed between a curved measurement surface and the web W. The dryers 22,23,24 are, for example, infrared, ultraviolet, microwave, radiation heating and/or induction heating dryers.

Counter radiators 25,26,27 are used, when needed. On the opposite side there may also be another radiator or an air dryer. When desired, the dryers may be profiling dryers. The tension profile of the web can also be affected by the arrangement in accordance with the invention, when placed before a coating station.