Finnish patent 106 277 discloses a sectional roll comprising a plurality of roll segments arranged adjacent in the axial direction, each roll segment mounted to rotate on bearings supported on a separate support shaft. Coupling members, such as a projection and a mating recess, are arranged on both axial end surfaces of the support shafts of the roll segments, which coupling members serve to disengagea- bly connect two successive roll segments to each other. The support shaft consists of at least two parts whose mutual disposition is alterable for the purpose of alter- ing the axial length of the support shaft so much that the coupling members of the end surfaces of two successive sectional rolls can be engaged and disengaged with each other. This arrangement makes it possible to change a single roll segment from the central area of the sectional roll without having to disassemble the entire row of roll segments. This known arrangement is especially concerned with the suitability of the sectional roll for use as a spreader roll. However, this known sectional roll construction is problematic in rider roll applications, because the gap between the roll shells of adjacent roll segments may cause web marking. The space between the roll shells is at least of the same extent as the width of the sup- port used for supporting the bearings of the roll segments, meaning that the width of the support of sectional rolls having a large diameter is great, which leads to a larger gap between the roll shells and thus to increased risk of web marking.

If a roll segment of a sectional roll needs to be changed, for example due to a de- fect in the bearing unit, in the sectional roll construction having a drive according to prior art the roll segments have had to be disassembled from the end all the way to the defective roll. The changing process is very laborious and requires realign- ment of almost the entire sectional roll. Due to these reasons a shutdown lasting up to 24 hours may in practice be needed for changing a single roll segment.

An object of the invention is to provide a non-marking, easy-maintenance sec- tional roll.

A further object of the invention is to provide a sectional roll suitable for use as a rider roll, particularly as a rider roll provided with a drive, preferably in a finish- ing machine of a paper or board web.

To achieve the afore-mentioned objects and those that come out later the sectional roll according to the invention is mainly characterized in what is presented in the characterizing part of claim 1.

In the sectional roll construction according to the invention an endless member evening out the point of discontinuity is arranged between the roll segments of the sectional roll, which endless member extends over at least part of the circumferen- tial dimension of the roll shell. The endless member extends most suitably over at least that part of the circumferential dimension of the roll shell which is covered by the web in the area of the roll in question. The endless member is most suitably a toothed belt, by means of which, according to a further advantageous feature of the invention, torque is transmitted between adjacent roll segments. Thus, accord- ing to the invention, the gap between the roll segments of the sectional roll is closed, due to which there is no marking of the web. In the construction according to the invention only one roll segment of the sectional roll will have to be disas- sembled and realigned in case of a bearing unit defect or belt-break, since no clutches preventing the dismounting of a centrally situated roll segment are needed between the roll segments. In the arrangement according to the invention a multigroove V-belt or flat transmission belt may also be used besides a toothed belt as the member evening out the point of discontinuity and, according to a fur- ther advantageous feature, transmitting the torque.

The sectional roll construction according to the invention is especially suitable for use as a rider roll of a paper or board machine, more particularly in connection

with finishing machines, e. g. different winders. It may also be advantageously applied in connection with, for example, the press device disclosed in Finnish patent 106 447. The sectional roll of the invention may also be used in other paper or board machine positions suitable for a sectional roll, for example as a guide roll of a felt, belt, wire and/or web.

The invention will now be described in more detail with reference to the figures of the accompanying drawing, to the details of which the invention is, however, by no means intended to be narrowly confined.

Figure 1 schematically shows a partially sectional side view of an application ac- cording to the invention.

Figure 2 schematically shows a sectional view along the line A-A in Figure 1.

Figure 3 schematically shows an application of the invention in connection with a wind-up.

Figures 1 and 2 schematically show an advantageous application of the invention, in which a sectional roll 20 consists of roll segments 10. An endless member 11, e. g. a belt, evening out a gap is arranged between the ends of rotating roll shells 13 of two roll segments 10, the member being a toothed belt in the application according to the figure. Both edges of the belt 11 are supported against the axial end surfaces of the roll shell 13, and the belt engages in toothed rims 12 arranged inside the roll shell, the toothed rims being connected by means of bearings 14 to support parts 15 of the roll segment 10, by means of which support parts 15 each roll segment 10 is supported against a framework (not shown) of the ma- chine/device. The belt 11 is an endless, loop-like member that circulates via the toothed rim 12, and a tightening ring (not shown) is arranged to the inner side of one end of the loop, and the tension of the belt 11 can be set as desired by tighten-

ing/loosening the ring. The belt can also be loosened for change by means of the ring.

The endless member 11 evening out the gap between the roll shells 13 extends over at least a part of the circumferential dimension of the roll shell and most ad- vantageously over the part covered by the web as it passes over the roll in ques- tion.

By means of the toothed belt 11 torque is transmitted between the roll segments 10 when using a sectional roll 20 provided with a drive, e. g. in rider roll applica- tions. Since the belt 11 evens out the gap between the roll shells 13, no gap is left between the roll segments 10 and there is no marking of the web. A single roll segment 10 can be changed by removing the belt 11, whereafter the roll segment 10 can be released from the construction in order to be changed by removing a coupling member 16 connecting the support parts 15 of adjacent roll segments 10, which coupling member is arranged inside the belt 11 between the toothed rims 12 and the bearings 15.

The drive of the sectional roll 20 is typically situated at one or both ends of the sectional roll 20. The torque is transmitted to the outermost roll segment of the sectional roll by means of a belt, e. g. a toothed belt, V-belt or a flat transmission belt or by means of a shaft/clutch arranged in the centre of the outermost roll segment. The drive of the sectional roll 20 can also be realized so that the torque of the drive is transmitted to the rolls by means of belt/belts situated between the rolls. These belts may share a drive or they may each have a separate drive. If several belts share a drive, the torque is transmitted by means of a shaft/shafts situated between the wheels rotating the belts.

A motor arranged in connection with the sectional roll 20 can be a drum motor in which case the motor is situated inside one roll segment of the sectional roll and the shell of the roll segment is rotated by means of the motor and the belts trans-

mit the torque between the roll segments. This application is used, for example, when there is no space to use a drive arranged outside the sectional roll.

An accelerating torque/a braking torque can be transmitted by means of the end- less member 11 from the drive of the sectional roll 20 to the roll segment 10. The torque transmitted by the endless member 11 can be used as a winding parameter of the wind-up. The surface speeds of the endless member 11 and of the roll seg- ments of the sectional roll 20 are substantially the same.

Most preferably a belt, e. g. a toothed belt, multigroove V-belt or a flat transmis- sion belt, is used as the endless member. The friction qualities of the surface of the endless member 10 and of the surface of the roll shells 13 of the roll segments 10 of the sectional roll 20 against the web are advantageously substantially simi- lar. The surface hardness of the endless member 11 and of the roll segments 10 of the sectional roll 20 may be substantially equal or the surface of the endless mem- ber is softer than the surface of the roll segments of the sectional roll. The surface of the endless member 11 may also be grooved.

Figure 3 shows a wind-up 30 in connection of which a sectional roll 20 according to the invention is arranged, in which sectional roll an evener member has been arranged between the ends of the roll shells of the roll segments of the sectional roll 20, which evener member covers at least a part of the gap corresponding to the portion covered by the web W as it passes over the sectional roll.

In this application a section 20 forms a nip N with a paper roll 25 being formed by means of the wind-up. In this application an endless member situated between the roll shells of the roll segments runs through the nip N and the outer surface of the endless member 11 and the roll shell 13 is substantially even at least cross- directionally at the nip. Rolls 25 are formed from a web W in a wind-up 30 around a winding core 26', which wind-up 30 is, in the situation illustrated in the figure, in a wind-up sequence change step, where there is a freshly completed roll

25 and the winding-up of a new roll is being started around the winding core 26'.

The roll is formed in a winding nip N'between a winding cylinder 27 and the paper roll being formed around the winding core 26'.

The invention has been described above only with reference one of its preferable exemplifying embodiments, to the details of which the invention is, however, by no means intended to be narrowly confined.