The invention also relates to a two-drum winder in which a paper web or equivalent is wound on support of two winding drums into a paper roll, in which winder the paper web is wound into a paper roll through a nip between a forward winding drum and the paper roll that is being formed, which forward winding drum and rear winding drum are mounted and supported at their ends by means of bearings.

From prior art, two-drum winders are known in which a paper web or equivalent is wound on support of two winding drums into a paper roll through a nip between one of the winding drums and the paper roll that is being formed. From prior art, centre- drive winders are also known in which a paper web is wound into a paper roll through a nip between a drum provided with a centre-drive or an equivalent drum and the paper roll that is being formed. One two-drum winder of this type is disclosed in the applicant's patent FI 70195 and, similarly, one centre-drive winder of this type is disclosed in the applicant's patent FI 942451 (WINROLL).

With increasing speeds of paper machines and with increasing widths of manufactu- red paper webs and thus with increasing sizes of paper rolls, the diameter of the winding drums has proved to be a problem, which diameters cannot be enlarged because of geometric limitations. On wide machines, the winding drums are dynami- cally flexible and their oscillation amplitude is relatively high, which increases deformation of the paper roll that is being formed and thus causes vibrations in winding, which in turn impairs runnability and increases premature wear of machine

components. The paper rolls formed in two-drum winders also tend to press the winding drums apart from each other, in which case, during winding, the centremost rolls drop downwards on the winding drums while the distance between them increases, and thus an even winding result is not obtained.

An object of the invention is to provide a solution to the problems in winding arising from the reasons set out.

An object of the invention is also to provide a winding device which has lower susceptibility to vibration and more rigid drums than in prior art arrangements.

An object of the invention is also to provide an arrangement in which the diameter can be chosen according to the rigidity of the drum and the properties of the drum without the central feature being determined by the problems caused by vibration.

With a view to achieving the objectives stated above and those that will come out later, the winding device according to the invention is mainly characterized in that a drum or equivalent is mounted in a longitudinal direction at at least one point in the middle of the drum or equivalent by means of bearings such that at least two component drums are formed.

The two-drum winder according to the invention is mainly characterized in that a forward winding drum and/or a rear winding drum is/are mounted and supported in a longitudinal direction by means of a bearing at at least one point in the middle such that at least two component drums are formed.

In the application in accordance with the invention, the drum/drums of the winding device is/are supported and mounted in a bearing in a longitudinal direction at one or more points, in which case the rigidity of the drum/drums increases manyfold. In two-drum winding, this leads to a considerable natural frequency difference in the drums of the winding drum, which reduces vibration. Furthermore, by using this arrangement it is possible to slightly reduce, if needed, the diameter of the

drum/drums and, correspondingly, when using a drum supported and mounted in a bearing in the middle in a longitudinal direction as a forward winding drum in a two-drum slitter-winder, the diameter of a rear drum may be increased, in which case the rigidity of the rear drum further increases and its susceptibility to vibration decreases. The drum supported in the middle in a longitudinal direction in accordan- ce with the invention may be the forward or the rear drum of a two-drum slitter- winder or both winding drums may be constructed on this principle. The drum arrangement in accordance with the invention is also suitable for use as the drum of a centre-drive winder.

In the following, the invention will be described in more detail with reference to the figures in the accompanying drawing, to the details of which the invention is by no means intended to be strictly confined.

Fig. 1 schematically shows a two-drum winder in which the drum in accordance with the invention is a forward drum.

Figs. 2A and 2B illustrate by way of example the principle of diameter changes underlying the invention in winding drums consisting of 2, 3 and 3 components.

Fig. 1 schematically shows winding drums 10,11 of the invention, the forward drum 10 of which is supported and carried in a bearing at two points in the middle such that the forward drum 10 is formed of three shorter component drums 10a, 10b,10c.

The rear drum 11 is supported and carried by means of bearings 21,22 at its ends.

The forward drum 10 is supported by means of bearings 23,24 at its ends and bearings 25,26 are placed in the middle of the forward drum 10 in a longitudinal direction.

In accordance with the basic idea of the invention, in addition to bearing support arrangements placed at the ends in a longitudinal direction, the drum used in winding is supported and carried in a bearing at at least one point between the ends of the drum. Preferably, the drum is mounted in a bearing and supported in a longitudinal

direction at points in such a way that component drums of substantially the same size are formed.

In the following, reference is made to Figs. 2A and 2B, according to which a steel winding drum having an outer diameter of 850 mm and a wall thickness of 50 mm is examined in an example. The width of the slitter-winder in the example is 10 m.

Figs. 2A and 2B show which outer diameters provide two- and threefold rigidity for a drum consisting of 2, 3 and 4 components as compared to that of a one-component winding drum.

Fig. 2A shows drum diameters providing twofold rigidity. The diameter D of the drum is denoted on the vertical axis and the number of component drums is denoted on the horizontal axis and the size of the diameter is denoted above the bar graph.

The unsquared area represents a drum the rigidity of which = K, and the squared area represents a drum the rigidity of which = 2K.

Similarly, Fig. 2B shows drum diameters yielding threefold rigidity, and the squared area thus corresponds to a drum the rigidity of which = 3K. The unsquared area, as above, represents a drum the rigidity of which = K.

As is apparent from Figs. 2A and 2B, by using the arrangement in accordance with the invention, a drum is provided the rigidity of which increases so as to be many- fold as compared to a drum not supported in the middle. When this kind of drum is used in a two-drum slitter-winder, a centre-drive winder or equivalent, the quality of the roll is improved while deformation and vibration of the roll decreases.

Moreover, the runnability of the winding device improves considerably.

The invention has been described above with reference to some of its preferred exemplifying embodiments only, to the details of which the invention is, however, not intended to be strictly confined. Many variations and modifications are possible within the scope of the inventive idea defined in the following claims.