Sealing arrangement for the roll end in a paper/board or finishing machine

The present invention relates to a sealing arrangement for the roll end of a paper/board or finishing machine, the said roll comprising a rotating roll shaft having a body part with a larger diameter, at both axial ends of which is formed a bearing shaft with a smaller diameter, which is rotatably supported in the bearing housing, and a roll mantle arranged around the body part at a radial distance from the outer surface of the body part, the said roll mantle being provided at both of its axial ends with an end flange extending in an essentially radial direction towards the bearing shaft to a distance from the outer surface of the bearing shaft, whereby a fluid chamber is formed between the outer surface of the body part and the inner surface of the roll mantle, the said chamber being essentially closed by means of end flanges.

The sealing arrangement of the invention is primarily intended for a roll in which the body part is cambered, while the mantle part is cylindrical. This type of roll is only intended to be loaded on the outside of the mantle with a force that straightens the camber in such a way that an even line load will prevail between the body and the mantle, which means that the cylindrical mantle is also essentially straight, that is, a deflection-compensated roll is in question, which is described in the present applicant's earlier Finnish patent application no. FI 20065824. When feeding a flowing medium, such as hot oil, into such chamber formed in a roll between the mantle and the body, for example, in order to heat the mantle, or a cooling medium to cool the mantle, sealing is required between the mantle and the body to allow movement of the parts being sealed with respect to one another. Due to the structure of the roll, the axes of rotation of the mantle and the shaft are mutually slightly offset. The problem with sealing is that the roll body deflects due to the load, but the mantle does not, which means that a continuous radial movement arises as the roll rotates. Moreover, the roll

mantle is arranged to rotate with the shaft when it is loaded and this effects a slight difference in the angular speed between the rotary movements of the mantle and the shaft, which will spin the sealing in the axial direction. The difference in angular speed leads to a speed difference between the surfaces being sealed, which may be, for example, about 30 mm/s.

The aim of the present invention is to provide a solution by means of which the stresses exerted on the seals can be minimised and thus the service life of the seals extended, and which solution is relatively economical and easy to implement for different sizes of diameter.

According to the first aspect of the invention, the sealing arrangement is characterised in that the sealing arrangement comprises a control flange attached to the end flange, the said control flange being able to move in a radial direction with respect to the end flange, guided by the relative movement between the bearing shaft and the roll mantle due to the deflection of the bearing shaft, and that in the control flange are arranged first sealing means that move with the control flange, which rest in the radial direction in a sealing manner against the bearing shaft, and second sealing means which rest in the axial direction in a sealing manner against the sealing face formed on the end flange.

A sealing arrangement according to a second aspect of the invention, on the other hand, is characterised in that the sealing arrangement comprises a seal mounting body arranged on the bearing shaft, to which body is attached a metal bellows making possible axial movement at the axial end on the body part side of the roll shaft of the mounting body, at the, with respect to the body part, outward free end of which metal bellows is a clamp for an end face seal, the said seal being supported in a sealing manner against the internal sealing face formed on the end flange.

A sealing arrangement according to a third aspect of the invention is in turn characterised in that the sealing arrangement comprises a sealing body fixedly attached by bearing means to bearing structures outside the roll, the said sealing body being located between the inner surface of the roll mantle and the outer surface of the bearing shaft, in the space between the inner surface of the end flange of the roll mantle and the axial end of the body part, and that in the sealing body are formed radially extending first sealing grooves on the outer surface on the inner surface side of the roll mantle, and second sealing grooves on the inner surface on the bearing shaft side, in which sealing grooves are placed corresponding sealing means in such a way that they may move in the radial direction guided by the relative movement between the bearing shaft and the roll mantle due to the deflection of the bearing shaft.

Equipped with the sealing arrangement according to the invention, the roll may be used, among others, as a belt guide roll on wide machines, as a thermo roll, as a cooled roll, or as a heated belt guide roll.

The invention is described in greater detail in the following, with reference to the accompanying drawings, in which:

Figure 1 shows an embodiment of the invention as a diagrammatic sectional view of one end region of the roll,

Figure 2 shows another embodiment as a diagrammatic sectional view of one end region of the roll,

Figure 3 shows yet another sealing arrangement as a diagrammatic sectional view of one end region of the roll,

Figure 4 shows still another sealing arrangement as a corresponding diagrammatic sectional view of one end region of the roll,

Figures 5-7 show some support arrangements for guide rolls used in a metal belt cycle, and

Figure 8 shows a roll arrangement in a metal belt calender as a diagrammatic view in principle.

In figures 1 to 4, the same reference numerals have been used for corresponding parts.

According to figure 1, the roll 1 comprises a roll shaft, which is comprised of a bearing shaft 4 mounted rotatingly in bearings in a bearing housing (not shown) and of a body part 3 with a larger diameter between the bearing shafts. Around the body part 3 is positioned a roll mantle 2 at a radial distance from the body part, whereby between the outer surface 12 of the body part and the inner surface 11 of the roll mantle is formed a fluid chamber which is closed essentially at its end regions by means of an end flange 9 attached to the roll mantle 2. In the embodiment shown, the end flange 9 is attached to the roll mantle by means of fixing screws 10. To prevent the flowing medium supplied in the chamber space from leaking, the end flange 9 is provided, through the gap between the end flange 9 and the roll shaft, with a control flange 7, which is attached to the end flange 9 with a ring fastener 8, by means of fixing screws 8a. The control flange 7 is dimensioned in such a way with respect to the ring fastener 8 that between them is formed a radial clearance allowing radial movement of the control flange guided by the relative movement of the roll mantle 2 and the roll shaft. In the control flange 7 are located the actual sealing means 13, 14, which may be, for example, inexpensive cord packings. The seals 13, 14 may be tightened axially against the sealing face formed on the end flange 9 and

radially against the sealing face formed on the bearing shaft 4 by means of a clamping sleeve 5 and clamping screws 6. This structure provides considerable advantages, including an inexpensive construction, easy implementation for different diameters and an uncomplicated possibility of tightening the seals in case of leakages. By means of the construction may also be achieved high heat resistance, even as high as 800 °C, and moreover, the structure is not easily breakable and is made relatively thin.

Figure 2 shows a sealing arrangement corresponding in principle essentially to Figure 1, where the seals are, however, arranged so that there are two in parallel, respectively, 13a, 13b, 14a, 14b, and on the bearing shaft 4 is additionally formed a separate sealing shoulder 4a, on which has been made a separate sealing face required by the radial sealing. In the embodiment of Figure 2, the end flange 9 and the ring fastener 8 are attached by joint fixing screws 10 to the roll mantle 2. Functionally, the solution of Figure 2 corresponds essentially to the solution of Figure 1.

Figure 3 shows yet another end sealing solution which differs functionally from the solution of Figures 1 and 2. In this solution, in the lower part of the end flange 9 is formed a collar 9a extending axially outwards and comprising a sealing flange 9b directed downwards, on the inner surface of which is formed a sealing face. On the bearing shaft 4 is formed a shoulder part 4a with a larger diameter, extending axially outwards from the body part 3, on which shoulder part is positioned a sealing body 19. On the sealing body 19 is formed, on the body part 3 side end of the roll shaft, a fixing shoulder 23 to which is attached a metal bellows 15 extending axially outwards and on the free outer end of which is attached a slide ring clamp 16 which supports the slide ring 18 in such a way that the slide ring rests in a sealing manner against the inner sealing face of the sealing projection 9b, loaded by the metal bellows 15. On the sealing body 19 is formed a groove 19a for preventing the rotation of the slide ring. The mounting body 19 is locked to

the bearing shaft 4a by means of a locking sleeve 17 having an internal thread which can be threaded to the end of the mounting body 19 provided with an external thread 21. Between the locking sleeve and the mounting body is a seal 20 supported in a sealing manner against the bearing shaft 4a to prevent leakages between the mounting body 19 and the bearing shaft 4a. This type of solution is particularly well suited for relatively high sealing sliding speeds.

Figure 4 shows still another sealing arrangement using a sealing body 32 solidly fixed via a support means 30 to support structures outside the roll, for example, a bearing housing. The sealing body 32 is located between the inner surface 11 of the roll mantle 2 and the outer surface of the bearing shaft 4, in the space between the inner surface of the end flange 9 of the roll mantle and the end of the shaft of the body part 3. In the sealing body are formed radially extending first sealing grooves 34a-34c on the outer peripheral surface on the inner surface 11 side of the roll mantle, and second sealing grooves 35a-35c on the inner peripheral surface on the bearing shaft 4 side. In these sealing grooves are located corresponding sealing means 31a-31c and 33a-33c, which may be, for example, carbon O-ring seals. The sealing means are dimensioned in such a way with respect to the sealing grooves that they will be able to move in the radial direction guided by the relative movement between the bearing shaft and the roll mantle due to the deflection of the bearing shaft. In the spaces between axially successive seals may be made bores 36 for possible leakage oil.

To ensure controllability in a metal belt calender, the steel belt must be kept sufficiently tight, which may be, for example, of the order of about 100 Mpa. The belt tension will, therefore, exert a force of up to 500 kN/m on the guide roll, which would result in considerable deflection of a wide size range (5-10 m) calender. This would lead to the belt having an uneven tension profile, where the edges would be tight and centre slack and this would hinder the

controlling of the belt and the process itself due to the changes in pressure exerted on the web in the CD direction. One alternative for reducing the deflection of the rolls is to enlarge the guide rolls, but this is an expensive solution. Large rolls also take up more space, which may complicate the positioning of the calender in confined lines in connection with replacements. Deflection compensation by cambering the guide rolls will at the same time correct the tightness profile of the belt, but may result in the belt slipping/wearing because cambering alters the peripheral length of the guide roll. When cambering the edges of the roll to a lower level, the length of the belt-roll contact on the edges will decrease, and since the belt has no shear strain capacity, the belt will slip. One alternative is to form guide rolls from deflection-compensated rolls, such as the rolls depicted in connection with Figures 1-4, in which case the rolls may additionally be cooled or heated.

Another alternative for reducing the deflection of the guide rolls is to arrange support means in accordance with Figures 5-7 to support the guide rolls 52 on the inner loop side of the belt 51 of the metal belt calender. The support means may consist of supporting rollers 53 or rolls which may be hard steel rolls, which are short and have a smaller diameter than the guide roll 52. The supporting roller 53 is supported by bearings on a fixed structure in the transverse direction of the machine, for example, as in Figure 7, or they may be supported against one another, for example, by means of a separate intermediate body 54, as shown in Figure 6. In Figures 5 and 6, reference numeral 50 denotes the backing roll of the belt, which may be a thermo roll, for example, a thermo roll as implemented in Figures 1-4. The fibrous web being processed is denoted by reference mark W.

Figure 8 shows a diagrammatic view in principle of a roll arrangement of a metal belt calender 80 providing a possible solution to the deflection problem. In the embodiment shown, the metal belt 86 backing roll 81 is an approximately 1.5 m steel thermo roll with a thick wall to make the deflection

caused by the belt tension and line load slight. Inside the belt cycle is located a second identical thermo roll 82, the deflection caused by the roll mass of which is opposite to the deflection caused by belt 86 tension. The belt is heated by this second thermo roll. As guide rolls 83, 84 are used swimming deflection-compensated rolls with a diameter within the range from 1.0 to 1.2 m. The guide rolls use glycol as oil and their temperature is about 100- 120 °C. They are not actually used to heat the belt, but the heating is used essentially only to prevent cooling caused by convectional losses. These guide rolls ensure that the tensile stress of the belt is uniform in the CD- direction. Inside the belt cycle may be arranged a nip roll 85 which is preferably a zone-adjustable deflection-compensated roll, which can be used to correct profile errors due minor differences in belt tension. The running of the calender may be carried out at a nip pressure of 0.10-0.15 MPa, at which the web heating phenomenon preceding the roll nip functions, but the deflection of the thermo roll in the belt loop is slight.