Abstract:
The roll of a paper/board machine or finishing machine has an inner elongated structure ( 11; 104 ) which is at least partly comprised of composite material, including reinforcing fibers in matrix material. The structure is preferably comprised of a combination of metallic material and composite material.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is a U.S. national stage application of International App. No. PCT/FI2005/050091, filed Mar. 18, 2005, the disclosure of which is incorporated by reference herein, and claims priority on Finnish App. No. 20045093, filed Mar. 23, 2004. 
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to the inner elongated structure of the roll of a paper/board machine or finishing machine, such as the shaft of a deflection-compensated roll or the suction box of a suction roll. 
     Current production paper machines run at speeds nearing 2000 m/min and machine widths come close to 11 m. The future development trend is to continue increasing these values. 
     Increasing both will bring about a changeover to dynamic dimensioning in current deflection-compensated rolls unless new ways are invented for manipulating the specific frequency of the roll so as to prevent the critical specific frequency from falling upon the running zone. A deflection-compensated roll comprises a stationary shaft and a shell arranged to rotate around it, the shell being supported on the shaft by loading elements which exert a loading force against the inner surface of the shell to load the shell towards the backing roll forming a nip with the said roll. In the modem, wider deflection-compensated rolls of calenders, it has been necessary to increase dimensioning by as much as four classes as a result of dynamic dimensioning, which incurs considerable additional expenses. The increase in roll mass also causes problems regarding crane capacity, especially in old mills. 
     In a suction roll, a perforated shell rotates fitted with bearings on thrust shafts. Inside the shell may be a single- or multi-chamber suction box, the apertures of which open—limited by sealing strips—onto the inner surface of the shell for directing the suction at a specific sector of the suction roll. At the ends of the roll are connectors by means of which external negative pressure can be connected to the suction box. While the negative pressure is connected, a vacuum is formed under the paper web through the wire or the felt. The pressure difference formed removes water from the web to the perforations in the shell or holds the web during transfer. The negative pressure in the chambers is determined in accordance with the intended use of the suction roll. A problem with suction rolls is the deflection of the suction box towards the inner surface of the roll shell while negative pressure is connected to the suction box. In this case, external pressure will deflect the suction box in the direction of its suction inlets, whereby the seals of the suction box are pressed more tightly against the inner surface in the central area of the roll shell, thus wearing the seals more in their center than on the edge zone. 
     In simplified form, the specific frequency of the roll is determined according to the following formula: 
               f   i     =         λ   i   2       2   ·   π   ·     L   2         ·       (       E   ·   I     m     )       1   /   2               
where
         λ is the support constant   L is roll width   EI is stiffness, and   and m is mass.       

     From this equation for specific frequency can be seen that its characteristics cannot be efficiently manipulated by any means other than by manipulating stiffness, when the mass remains approximately constant. Another way of eliminating the detrimental effects of the vibrations themselves is to provide so high roll-internal damping that specific frequencies will not be a disadvantage. The aim of the present invention is to provide a solution by means of which the above-mentioned problems can essentially be eliminated. 
     To achieve this aim, the solution relating to the invention for realizing the inner elongated structure of the roll of a paper/board machine or finishing machine is characterized in that the structure is comprised at least partly of composite material, including reinforcing fibers in matrix material. 
     SUMMARY OF THE INVENTION 
     According to a preferred embodiment of the invention, the inner elongated structure of the roll is the stationary shaft of a deflection-compensated roll having a frame part essentially of fiber-reinforced composite, on which frame part is formed a support part of steel extending in the longitudinal direction of the shaft for supporting the loading elements bearing the shell on the shaft. According to another preferred embodiment of the invention, the inner elongated structure of the roll is the stationary shaft of a deflection-compensated roll having a frame part essentially of metal, which is coated with fiber-reinforced composite material. According to yet another preferred embodiment of the invention, the structure is a suction box inside the suction roll, which is preferably made completely of composite material. 
     Composite material refers to a structure comprising reinforcing fibers, for example, carbon, boron or glass fibers or their mixtures, and a matrix material, which may be polymeric, ceramic or metallic. Ceramic material comprises different oxides and carbides, such as AI—, B—, Cr—, Ti—, Si—, Sn—, W—, Zn—, Zr— oxides and carbides or their mixtures, and different nitrides, such as Bn and Si 3 N 4 . 
     The invention is described in greater detail in the following, with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a prior art deflection-compensated roll as a diagrammatic longitudinal section. 
         FIG. 2  is a cross-sectional view of the roll of  FIG. 1  taken along section line II-II. 
         FIG. 3  shows a deflection-compensated roll according to the invention as a diagrammatic longitudinal section. 
         FIG. 4  is a cross-sectional view of the roll of  FIG. 3  taken along section line IV-IV. 
         FIG. 5  shows the end section of the roll of  FIG. 3 . 
         FIG. 6  shows the end section of  FIG. 5  as seen in the direction of arrow VI. 
         FIG. 7  shows a diagrammatic longitudinal section of the end section of another deflection-compensated roll realized according to the invention. 
         FIG. 8  shows a modification of the embodiment of  FIG. 7 . 
         FIG. 9  shows a longitudinal section of yet another end section of a deflection-compensated roll according to the invention. 
         FIG. 10  shows a view of the roll of  FIG. 9  as seen from the end with the roll end removed. 
         FIG. 11  shows a diagrammatic cross-section of yet another deflection-compensated roll according to the invention. 
         FIG. 11   a  is an enlarged fragmentary view of the apparatus of  FIG. 11  taken at the circle  11   a.    
         FIG. 12  shows a diagrammatic cross-section of yet another deflection-compensated roll according to the invention. 
         FIG. 12   a  is an enlarged fragmentary view of the apparatus of  FIG. 12  taken at the circle  12   a.    
         FIG. 13  shows a diagrammatic longitudinal section of a prior art suction roll. 
         FIG. 14  shows a diagrammatic cross-section of the suction roll of  FIG. 13 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIGS. 1 and 2  show diagrammatically a prior art deflection-compensated roll  10  comprising a stationary roll shaft  11 , around which a roll shell  12  is arranged to rotate. The roll shell  12  is supported on the roll shaft  11  by means of hydraulic loading elements  17 . The hydraulic loading elements act in the direction of the nip plane, and by means of them, the nip profile of the roll can be controlled in the longitudinal direction of the roll. The roll shaft  11  is connected to the roll&#39;s support structures by means of shaft journals  18 . In the example disclosed, the roll  10  is provided with slide bearings  14 ,  14   a  acting on the main loading plain of the roll, whereby the bearings  14  act in the direction of the nip, that is, in a direction opposite to the loading direction, and the bearings  14   a  act in the opposite direction with respect to these. The roll further comprises lateral slide bearings  15 ,  15   a , which act in a transverse direction with respect to the main loading direction, and axial slide bearings  16 ,  16   a  acting in the axial direction, which rest on the roll ends  13 , and  13   a , respectively, through a lubricant film. Slide bearings  14 ,  15 ,  14   a ,  15   a  acting in the radial direction, rest, for their part, against the inner surface of the roll shell  12  through the lubricant film. A roll of this type is known, for example, from U.S. Pat. No. 5,509,883, and is thus not described in greater detail in this connection. 
       FIGS. 3 to 6  show a deflection-compensated roll realized according to the invention, where the same or similar parts are referred to by the same reference numerals as in  FIGS. 1 to 2 . In this embodiment, the roll shaft  11  is comprised of a beam, essentially I-shaped in cross-section, which is made of composite material, preferably of carbon fiber reinforced material, by lamination. In the upper part of the beam  24  is formed a longitudinal groove, in which a support part  26  of steel or cast iron is positioned by means of an intermediate layer. The intermediate layer  25  evens out differences in thermal expansion and fixes the support part to the fiber-reinforced frame  11 . On the support part  26  are formed bores for hydraulic loading elements  17 . Reference numeral  27  denotes a feed pipe for supplying hydraulic medium to the chamber beneath the loading element  17 . On the bottom part of the I-beam have been added fiber-reinforced plates  21 ,  22 ,  23  to areas requiring additional stiffness, as determined on the basis of the moment of deflection. The stiffening plates  21 - 23  can be joined together and to the I-beam, for example, by means of gluing with matrix material or by means of a bolted joint. The I-beam is connected to the thrust shaft  40 , for example, in the manner shown in  FIGS. 5 and 6 . The thrust shaft  40  comprises an inwards directed roll fixing part  41  to which are formed the protruding ends  11   a ,  11   b  of the I-beam, and grooves for receiving the web part between them. The interlocking of the I-beam and the thrust shaft is secured by bolted joints  42 , the said bolts extending from the level  43  formed on the upper surface of part  41  to the recesses  45  and  46 , the said recesses being arranged to lighten the thrust shaft. Locking may also be carried out, for example, by gluing instead of by bolted joints. The stresses exerted on the joint are not very high because the moment of deflection is small compared with the central part of the beam. This solution makes possible the relatively simple assembly of the roll. Depending on the loading forces, the upper part  24  of the I-beam may also be made completely of steel or cast iron, in which case no separate intermediate layer  25  or support part  26  will be required. An upper part of steel or cast iron may also be fixed, for example, by gluing with matrix material to the fiber-reinforced frame  11 . It is also conceivable to make the shaft completely of composite material. 
       FIG. 7  shows another deflection-compensated roll realized according to the invention, wherein the frame of the roll shaft  11  is steel and forms an integrated structure with the shaft journal  18 . The frame part is lightened in the area between the end sections where it is comprised of a relatively thin support part  11   a , which receives the compressive stresses. Nip loads cause compressive stresses on the shaft on the loading element  17  side, and tensile stresses on the lower part. To receive the tensile stresses, between the end parts of the shaft are arranged fiber-reinforced bars or plates  30  running through the end parts and locked in place by locking means  31 , which is a locking nut in  FIG. 7 . The bars or plates  30  are preferably of carbon fiber reinforced composite. 
     The embodiment of  FIG. 8  differs from that of  FIG. 7  only as regards the locking means  32 , which are made by winding of reinforcing fibers and by fixing with matrix material to the bar or plate  30 . 
     In the embodiment according to  FIGS. 9 and 10 , on the end parts of the roll shaft are formed mounting projections  36 ,  38 , and opposite end parts are joined with each other by means of reinforcing fibers dipped in matrix material and wound in the longitudinal direction of the shaft, which form bundles  35 ,  37  of composite material which receive the tensile stresses. Using the mounting projections makes it possible to wind the reinforcing fibers into one loop, whereby the strength of the structure is better than when using, for example, the separate locking means according to  FIGS. 7 to 8 , where the joint becomes weaker than the basic materials, whereby the structure must be dimensioned according to the strength of the joint. In the solution according to  FIGS. 9 and 10 , dimensioning takes place in accordance with the composite material and shaft material, for example, steel or cast iron. 
     An additional advantage in the embodiments of  FIGS. 7 to 10  is the free space remaining also on the neutral axis which may be utilized in positioning the hydraulic pipes of the loading elements. 
       FIGS. 11 ,  11   a ,  12  and  12   a  show some further embodiments of the deflection-compensated roll according to the invention, with the elimination of disadvantageous vibration as the starting point. This has been realized by adding a coating  50  of composite material on the existing roll shaft  11 .  FIG. 11  shows a diagrammatic, cross-sectional view of a deflection-compensated roll provided with an almost round-profiled shaft  11 , and  FIG. 12  shows a deflection-compensated roll with a so-called movable shell, the shaft of which is essentially rectangular in cross-section. Reference numeral  14   b  denotes the bearing means of the roll. 
     The coating  50  may be formed, for example, by providing the shaft first with a base treatment, for example, with glue, and by then winding a reinforcing fiber layer of, for example, glass fiber or carbon fiber, around the shaft, and by adding the matrix material to the reinforcing fiber layer. The addition of matrix material can be carried out, for example, by dipping the fibers to be wound in matrix material before winding, or by spraying matrix material on the surface of the shaft while winding the fibers. After coating, bores for the loading elements  17  and bearing elements  14   b  may be finishing cut on the shaft through the coating, and the means to be fixed on the shaft, such as oil collection means, may be added. Coating made by winding also makes possible relatively easy coating of shafts provided with straight surfaces ( FIG. 12 ). 
       FIG. 13  shows a view in principle of a prior art suction roll without an internal suction box. The suction roll comprises a roll shell  111  which is fitted with bearings to rotate on shaft journals  113 A and  113 B which are connected to the roll shell  111  through end flanges  112 A and  112 B. The roll shell  111  has a perforation comprised of numerous apertures  115  extending through the roll shell  111 .  FIG. 13  shows only a part of the perforation of the shell  111 . At least one of the shaft journals  113 B comprises connectors leading to the interior of the roll, to which an external negative pressure source (not shown) can be connected. By means of the negative pressure source, air is sucked out (arrow P 2 ) through the sector formed by the suction box, whereby a corresponding amount of air (arrow P 1 ) will flow inside the roll through the perforation of the roll shell. 
       FIG. 14  shows the suction roll of  FIG. 13  in cross-section and with the suction box mounted inside it. The suction box  104  and the seal holder part  105  are rigidly fixed to each other. The seals  101  are loaded against the shell  111  by means of loading tubes  103 , whereby the seals are made to press against the shell at approximately constant pressure even when the suction box is in a deflected situation. Because of the seal pressure, water lubrication V is necessary to reduce wear on the inner surface of the roll shell. When negative pressure is switched on in the suction box  104 , it deflects towards the inner surface of the shell. Deflection is strongest in the longitudinal central area of the roll, while the ends of the suction box remain in place. Nowadays, suction boxes are usually made of relatively thin sheet metal, whereby increasing rigidity by increasing thickness would increase weight which is not desirable. The deflection of the suction box can be reduced in accordance with the invention by making, for example, the seal holder part  105  or the entire suction box  104  of composite material, which makes possible greater rigidity with less weight.