The present invention relates to a roll for a web forming machine, which roll includes a shell, with end pieces at both ends of it to support the roll rotatably in the web forming machine, which end pieces are arranged to be detachably attached at each end of the shell, and in each of which end pieces there is an end plate with a protruding shaft in it for a bearing arrangement. The invention also relates to a method for manufacturing a roll for a web forming machine.

In a roll in a modern web forming machine, for example a paper or board machine, the shell and its end pieces are separate pieces. Thus they can be made separately and finally balanced in connection with the assembly of the roll, or afterwards. The known end pieces are manufactured by machining from cast pieces. Due to the manufacturing technique in question, the end piece becomes large and heavy. In addition, there are several labourious stages in manufacture. When the end piece is a single piece, the dimensioning of the end piece and the protruding shaft must take into account the manufacturing- technique limitations of both structures. For example, the casting technique requires the end plate to be dimensioned to be unnecessarily thick. In addition, a cast end piece is poor in terms of vibration. Particularly the protruding shaft bends more than the rest of the roll, which increases vibration in the roll during operation. In practice, the flexibility of the end pieces differs from that of the shell while the end piece also has no damping ability at all.

The invention is intended to create a new type of roll for a web forming machine, which is not only lighter than previously, but is also stiffer and superior in terms of vibration. The invention is also intended to create a new type of method for manufacturing a roll intended for a web forming machine, which is simple and which can be applied in the manufacture of different kinds of roll. The characteristic features of the roll according to the present invention appear in the accompa¬ nying Claims 1 and 12. Correspondingly, the characteristic features of the method according to the invention appear in the accompanying Claim 14. In the roll according to the invention, there is a new type of end piece, which is considerably stiffer than before relative to its weight. Thus the rotational speed of the roll can be increased without vibration becoming too great. The end piece is formed from several different parts, which are additionally attached to each other in a new way. In practice too, the parts can be dimensioned optimally nearly independently of each other while the finished construction is, in addition, light. Further, various functions can be arranged in the end piece, which in the prior art would be difficult and even impossible to implement. Using the method according to the invention, the deflection of the roll and through it the vibration can be controlled. At the same time, the roll can be rotated at a higher rotational speed than before. In the manufacture of the roll it is also possible to use new types of material and manufacturing methods.

In the following, the invention is examined in detail with reference to the accompanying drawings showing some embodiments of the invention, in which

Fxgure Ia shows an axonometric view of the roll according to the invention, Figure Ib shows the end piece of the roll according to the invention, Figure 2 shows a partial cross-section of the end piece of the roll according to the invention, Figure 3 shows a partial cross-section of part of the roll according to the invention, Figure 4 shows a cross-section of a second embodiment of the end piece according to the invention, Figure 5a shows a partial cross-section of the rope sheave of the roll according to the invention, Figure 5b shows an axonometric view of the rope sheave of Figure 5a, Figure 6 shows a cross-section of a second embodiment of the rope sheave of the roll according to the invention.

Figure 1 shows the roll according to the invention, which is intended for a web forming machine. Usually, the web forming machine is a paper or board machine, in which the roll is used, for example, as a guide or nip roll. Generally, the roll includes a shell 10 with end pieces 11 at both of its ends, for supporting the roll rotatably in bearing arrangements 12 in the web forming machine. The shell can be a cast shell or a shell made from a sheet material. The shell can also have surface treatment or a cover. Figure Ib shows the end piece 11 accord¬ ing to the invention, which is generally fitted detachably onto each end of the shell. In the end piece 11, there is an end plate 13 with a protruding shaft 14 in it for the bearing arrangement. In the end plate 13, there are also holes 15 for attachment bolts 16. There are more holes than are required for the attachment bolts, so that balancing bolts and/or masses can be attached to them at suitable positions.

Figure 2 shows the end piece 11, which includes a separate inner piece 17, in greater detail. In the inner piece 17, there is an internal hole 18 corresponding to the protruding shaft 14, for attaching the protruding shaft 14. In addition, the end plate 13 is supported on the inner piece 17 by at least one plate piece 19. Thus the various parts of the end piece can be manufactured separately, thus avoiding casting and machining large pieces. In addition, the parts can even be made in different ways and from different materials. Thus allowance can be made, for example, for stresses arising from the loading, or for surface roughness requirements. In the embodiment of Figure 2, the end piece 13, the protruding shaft 14, and the inner piece 17 are separately machined bodies of revolution. Thus their manufacture is simple and they can be dimensioned precisely for their operating purposes. For example, the tolerance between the parts can be made accu¬ rately. Mainly thanks to the plate piece, a thin end plate can be used, which will substantially reduce the weight of the end piece. Despite the thin structures, the end piece is stiff, because the various parts form a cell structure. Other advanta- geous features of the cell structure are presented later. In Figure 2 the protruding shaft 14 and the inner piece 17 are fitted to each other with a shrink-fit joint. Thus their mutual positioning is retained precisely and the protruding shaft can, if necessary, be replaced. This is thus preferably a question of a force-fit joint, in which force is transmitted with the aid of the friction in the joint surfaces. If necessary, it is also possible to use other forms of joint, such as a keyed joint.

The plate piece is manufactured from one or more plate parts and the end plate and the inner piece are arranged coaxialIy relative to each other. Thus it is easy to attach the various parts to each other while the finished end piece is accurate in shape and its dimensions, which reduces the need for finishing machining and also facilitates the balancing of the roll.

In the end piece 11 shown in Figure 2, the end plate 13 is a circular plate, in which there is an installation hole 20 for the inner piece 17. Thus it is easy to align the end plate 13 and the inner piece 17 with each other. In addition, the plate piece 19 is arranged to extend to the opposite end of the inner piece 17 to that with the end plate 13. Thus, together with the end plate and the inner piece, the plate piece forms a conical triangular cell, the totality of which is extremely stiff, despite the thin structures. The free length of the protruding shaft is also substantially reduced. In other words, the protruding shaft and the entire end piece deflect considerably- less than the known construction, which also reduces vibration in the roll.

The plate piece according to the invention is thus arranged as a cone. In the embodiment of Figure 2, the conic angle α opens towards the shell. In practice, the conic angle a is 45 - 140°, preferably 55 - 130°. Thus sufficient support is created for the protruding shaft, while the total length of the end piece remains reasonable. An increase in the diameter of the shell will naturally increase the conic angle. The dimension of the inner piece is, for its part, limited by the joint between it and the protruding shaft. Figure 4 shows a second embodiment of the end piece 11 according to the invention. In this case, the end plate 13 is in fact a circular ring 21 and the end piece 11 includes a second plate piece 22. In practice, the second plate piece 22 is thus arranged as part of the end plate 13. In addition to the above, the conic angle formed by the plate piece is, in this case, arranged to open away from the shell. This avoids the effect of the end piece in lengthening the roll, so that the roll can be fitted in even cramped positions. In other words, the roll can be made as short as possible. In Figure 4, the end piece 11 is arranged to be attached to a special ring piece 23, to which the shell of the roll is intended to be attached. Thus nearly the entire end piece can be fitted inside the shell and the bearing arrangement attached to the very end of the protruding shaft. Thus the free length of the protruding shaft is short and correspondingly the deflection of the protruding shaft is small . The term free length refers to the distance between the bearing arrangement and the first support point of the end plate, over which the protruding shaft can deflect. On the other hand, the bearing arrangement too permits a slight variation in the axial angle of the protruding shaft. The same reference numbers are used for functionally similar components. In addition to stiffness and lightness, the cell structure can also be exploited to create damping or insulating in the end piece. Even a purely air-filled end piece will insulate, for example, from the evaporation of heat in a dryer cylinder better than a solid-cast end piece. By arranging the end piece to be gas-tight, other gases or a mixture of them can be used. On the other hand, when using solid or foam materials, not only insulation but also effective damping will be created. For example, extruded foam can be easily led into the cell struc- ture while the foam will fill even the smallest recesses evenly. Figure 2 shows an end piece 11 filled with a foam-like material 24. Thus in general a damping and/or insulating material is arranged in the space delimited by the end plate, the inner piece, and the plate piece, which is impossible in the prior art. When the foam adheres to the delimiting parts, it will further reinforce the structure of the end piece.

Figure 3 shows a combination of the embodiments described above, in which two plate pieces 19 and 22 are used, but with the conical angle opening towards the shell. In this embodiment too, the use of the conical end piece 11 reduces by nearly half the free length of the protruding shaft 14. In addition, the protruding shaft 14 shown extends through the bearing arrange¬ ment 12 and has a keyway 25 for a drive motor or gearbox. In many modern web forming machines rope threading is used in addition, to carry the web-threading tail through the web forming machine when starting production. For the rope, a rope sheave is used in connection with many rolls, and carries the rope according to the shell. For the new type of end piece, the roll according to the invention includes a rope sheave, which is arranged to extend axially from the free length of the protruding shaft to the end plate. According to Figure 3, the plate piece 19 then remains inside the rope sheave 26. On the other hand, some conventional rope sheave can be used in connection with the roll shown in Figure 4. The rope sheave 26 according to the invention includes a bearing 27, which is arranged around the protruding shaft 14, but mechanically separate from it. In practice, the rope sheave thus has its own bearing, the inner ring of which is fitted around, but separate from the protruding shaft. The inner ring 28 of the bearing 27 thus does not move and is here supported by a separate support 29 on the plinth 30 of the bearing arrangement 12. In the outer ring 31 of the bearing 27 there are correspondingly attachment bolts 38, by means of which the sheet-material rope sheave 26 is attached to the bearing 27. Thus various rope sheaves of different sizes can be attached to the bearing. Thanks to the separate bearing, between tail threadings, the rope and the rope sheave with it can rotate at a crawl while the roll rotates at production speed. This saves energy and particularly the rope and the bearing of the rope sheave.

According to the invention, the part of the rope sheave 26 shaped according to the end piece 11 is a spun plate part 32. Thus a piece with a precise shape and dimensions, which has additionally good loadability, is created from a sheet mate¬ rial. Thus, despite the one-sided bearing arrangement, the rope sheave maintains its position and shape well. In addition, the plate part 32 includes a roll-formed portion 35 for the rope. According to the invention, the portion 35 is of the same sheet material as the plate part 32 or the separate additional part 34 attached to the plate part 32. In Figures 3 and 5a, the groove 35 for the rope is finally formed by roll forming in the spun plate part 32. In the embodiment in question, the diameter of the rope sheave is about 450 mm. Correspondingly, Figure 6 shows another embodiment of the rope sheave, which is intended particularly for large rope sheaves. In this case, a separate roll-formed additional part 34 is used, being attached to the spun plate part 32. Figure 6 shows two plate parts 32 and 32', the inner one of which can even be omitted in practice. Radial support plates can be used to stiffen the rope sheave. In Figure 6, the support plates 36 are attached to the outer plate part 32. The rope sheave shown is designed with a diameter of 1830 mm and the plate parts 32 and 32' used in it have a thickness of 2 - 3 mm. Thus even a large rope sheave will be light, but stiff. In practice, the mass of the rope sheave according to the invention is only one quarter of that of known rope sheaves. In addition, the smooth shape and closed struc¬ ture effectively prevent dirtying of the rope sheave. The rope sheave according to the invention can also be used in connec- tion with rolls equipped with conventional end pieces.

When using an end piece according to the invention in the manufacture of a new roll, the roll can be dimensioned for a higher rotation speed than previously, without vibration problems. The end piece according to the invention can also be placed in existing rolls . In the method according to the invention, the roll is first detached from the web forming machine, after which the end pieces are removed from the shell. End pieces according to the invention are then attached to the shell and finally the roll is reattached to the web forming machine. In addition, prior to installation the roll can be balanced and, for example, surfaced. Using the method in question, a roll, which can be rotated at a higher speed than before, is created rapidly and economically. Thus in rebuilds the replacement of the end pieces will be sufficient, assuming that the other components, such as the drive motors and bearing arrangements are suitable for increasing the speed. When manufacturing new rolls, the end pieces are attached to the shell and the roll is installed in the web forming machine.

The vibration of a new or refurbished roll can be brought under control, for example, by minimizing deflection, in the end pieces according to the invention, the length of the protruding shaft has been clearly shortened by arranging the plate piece to be conical and by extending the inner piece of the plate piece from the end opposite to the end plate to the end plate. This creates a triangular cell structure, which is stiff and additionally supports the protruding shaft effectively. The properties of the end piece can be further altered or improved by arranging damping and/or insulation in the end piece. Figure 2 shows in addition a feed-through pipe 37, through which leads to measuring devices, for example, can be taken inside the roll. On the other hand, it is also possible to install measuring devices, or their auxiliary devices, such as telemet- ric devices' transmitters (not shown) inside the cell struc- ture.

The cast parts, for example, the inner piece and the protruding shaft, are made by traditional methods by casting and machin¬ ing. In the manufacture of the plate piece, however, laser cutting, spinning, and/or roll-forming are used. In manufac¬ ture, it is even possible to use thin sheet material, with a thickness of less than 3 mm. Besides being shapable, sheet material can be laser-welded with good results. According to the invention, the plate piece is indeed attached to the inner piece and to the end plate by laser-welding. The weld point is shown by small arrows in Figures 2 and 4. In practice, the plate piece can also be made from several different parts by welding, though it is preferably to make small plate pieces from a single sheet. The methods described above are also applied in the manufacture of the rope sheave, which rope sheave is attached by bearings separately from the protruding shaft. The vibration of a totality created in this manner will be small and the rope sheave will be precisely supported.

The roll according to the invention and particularly its end piece is light but stiff compared to a corresponding cast piece. By using a light but stiff end piece, the dimensioned speed of a roll can be increases by as much as 5 - 20 %. This largely due to the new type of end piece, by means of which the entire roll is made stiffer than before. The specific frequency of the roll then increases, when its vibration sensitivity decreases. In tested rolls, the specific frequency has in¬ creased by 5 - 10 %, in some cases by as much as 20 %. In addition, the protruding shaft can be selected with more freedom than before, so that it is possible to use smaller shaft diameters than previously. At the same time, the choice of bearing becomes freer. In addition to the above, the cellular end piece is considerably cheaper to manufacture than a cast piece while it can incorporate damping, insulation, or both.