Patent Publication Number: US-7900330-B2

Title: Method and device for changing a fabric in a paper or board machine

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     This application is a U.S. national stage application of International App. No. PCT/FI2006/050121, filed Apr. 3, 2006, the disclosure of which is incorporated by reference herein, and claims priority on Finnish App. No. 20055152, filed Apr. 5, 2005. 
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT 
     Not applicable. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a method and a device for changing a fabric in a paper or board machine. 
     FI patent 103421 discloses a method and a device for changing a fabric in a paper machine. In the method, frame beams of the tending side are moved to a position in which a gap is formed in the vertical frame beams and the fabric is changed through said gap. In the method, the frame parts of the frame beam are raised by an actuator onto support of a device comprising a set of rollers and the fabric is passed through the gap into a throat of the set of rollers. The set of rollers serves as a fabric-pulling device during the change process and after the change the vertical frame beams are lowered onto backing surfaces of the frame parts. 
     This kind of device formed of a set of rollers comprises a very large number of separate parts, even thousands of parts. The assembly of the device is time-consuming, maintenance is expensive, and the large number of parts additionally reduces the reliability of operation of the device. 
     The arrangement in accordance with the invention aims to reduce problems associated with the arrangements of the state of the art. 
     SUMMARY OF THE INVENTION 
     The device according to the invention includes a very small number of separate parts, a few tens of parts. The device is therefore easy to assemble, inexpensive to maintain and its reliability in operation is good. 
     A pressure medium between a pressure chamber and a band of the device applies a very even pressure to a fabric passing between bands. The caterpillar track of the set of rollers in accordance with the state of the art is formed of a large number of short pieces, so that a small gap remains between the pieces where pressure on the fabric between the caterpillar tracks is zero. Thus, caterpillar tracks cause an uneven pressure on the fabric passing between the caterpillar tracks. 
     The definition “paper or board machine” includes in this application all machines and devices that are associated with the manufacture of paper and board and have changeable fabrics, such as paper machines, board machines, tissue machines, pulp machines and belt calenders. 
     In the following, the invention will be described in detail with reference to the exemplifying embodiments shown in the figures of the appended drawing, to the details of which embodiments the invention is not meant to be limited. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of frame structures of a press section when viewed in the machine direction. 
         FIG. 2  is an axonometric view of the device in accordance with the invention for changing a fabric. 
         FIG. 3  is an axonometric view of one unit of the device in accordance with the invention. 
         FIG. 4  is an axonometric view of a variant of the device illustrated in  FIG. 3 . 
         FIG. 5  shows a pressure chamber of the device in accordance with the invention in a top view. 
         FIG. 6  is a sectional view of the pressure chamber and seals placed in it in a situation in which the pressure chamber is unpressurized. 
         FIG. 7  is a sectional view of the pressure chamber and seals placed in it in a situation in which the pressure chamber is pressurized. 
         FIG. 8  is an axonometric view of an application of the device of the invention provided with a protective frame. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  is a sectional view of frame structures of a press section when viewed in the machine direction. Support beams T extend between load-bearing beams R from a tending side HP to a driving side KP. Fabric feed devices  100 ,  200  are mounted in the load-bearing beams R of the tending side HP. 
       FIG. 2  is an axonometric view of the fabric feed device  100 ,  200  in accordance with the invention. The device is formed of two units  100 ,  200  placed one on top of the other. 
       FIG. 3  shows one unit  100  of the device in accordance with the invention. Each unit  100 ,  200  comprises a first side frame  101  and a second side frame  102  spaced from the first side frame. The side frames  101 ,  102  are substantially rectangular, elongated pieces. A first roller  110  is attached to first ends  101   a ,  102   a  of the side frames  101 ,  102 , and a second roller  120  is attached to second ends  101   b ,  102   b  of the side frames  101 ,  102 . An endless band loop  130  rotates around the rollers  110 ,  120  and runs between the side frames  101 ,  102 . Shafts  111 ,  121  of the rollers  110 ,  120  are attached to bearing housings  112   a ,  122   a , and the bearing housings  112   a ,  122   a  are in turn attached to the ends  101   a ,  101   b  of the side frames  101 ,  102 . The height h of the side frames  101 ,  102  is slightly greater than the diameter of the rollers  110 ,  120  plus the thickness of the band  130  multiplied by two. The first  110  and/or the second  120  roller can be provided with a drive, for example, by means of a drive motor arranged inside the roller  110 ,  120 . A pressure chamber  300  is disposed between the side frames  101 ,  102 , the band  130  running over said pressure chamber. The side frames of the upper unit  200  of the device are attached to a load-bearing beam R of the tending side HP of the machine on the upper side with respect to the device, and the side frames  101 ,  102  of the lower unit  100  of the device are attached to a load-bearing beam R of the tending side HP of the machine on the lower side with respect to the device. The side frames  101 ,  102  of the units  100 ,  200  of the device can be attached to each other when the machine is operated, for example, by means of eye nuts suitable for the purpose and easy to detach in connection with a fabric change (not shown in the figures). 
       FIG. 4  shows a variant of the unit shown in  FIG. 3 . In this embodiment, a roller  110  is used only at one end of the unit. At the opposite end there is, instead of a roller, a curved surface  125 , over which a band  130  runs. In this case, a drive is in the roller  110  situated at the one end of the unit. 
       FIG. 5  shows a pressure chamber  300  in a top view. The pressure chamber  300  is formed of a rectangular piece attached at its edges to the side frames  101 ,  102  of the unit. A rectangular groove  301  having rounded corners is formed in that surface of the pressure chamber  300  which is positioned against the inner surface of the band  130 . In the area defined by the groove  301  within itself there is an inlet opening  302  for a pressure medium. At the inner edge of the groove  301  there is a first seal holder  330  and at the outer edge of the groove  301  there is a second seal holder  340 . The seal holders  330 ,  340  are fixed by fixing means, preferably by screws  331 ,  341  to the pressure chamber  300 . 
       FIGS. 6 and 7  show a cross-section of the groove  301  of the pressure chamber and of the seals placed in the groove.  FIG. 6  depicts the pressure chamber in a rest position, i.e. in an unpressurized position, and  FIG. 7  depicts the pressure chamber in a pressurized position. A first seal  310 , whose cross-section is substantially round, i.e. it can also be a rounded polyhedron, is mounted on the bottom of the groove  301  having a rectangular cross-section. A second seal  320 , whose cross-section is substantially in the shape of an inverted letter T or a shaped joint with shoulders limiting the displacement of the seal by means of the shoulders in a corresponding manner, is mounted on the first seal  310 . This second seal  320  forms a slide seal for the steel band  130 . In the rest position the first seal  310  is compressed, whereby it produces a lifting force for the second seal  320 . This lifting force presses the second seal  320  into contact with the inner surface of the band  130 . When a pressure medium is fed from the pressure medium inlet opening  302  shown in  FIG. 5  into the pressure chamber, the pressure medium spreads into a space between the surface of the pressure chamber and the band  130  and further into the groove  301 . In the groove  301  the pressure medium causes a lifting force for the second seal  320 , whereby the second seal  320  rises upwards in proportion as the pressure medium raises the band  130  and the load situated on the band. When shoulders  320   a ,  320   b  of the second seal  320  come into contact with the seal holders  330 ,  340 , the rising movement of the second seal  320  stops. Then, an increase in the pressure of the pressure medium no longer raises the band  130  and the load on it, but, instead, the pressure medium discharges from between the second seal  320  and the band  130  out of the pressure chamber. A slide surface is thereby formed of the pressure medium between the second seal  320  and the band  130 , the band  130  sliding almost without any friction over the second seal  320 . 
     In accordance with the application shown in  FIG. 8 , the device of the invention can be provided with an outer frame  400 , which forms a protection for the device according to the invention. The outer frame  400  comprises an upper frame  410  and an extension part  420  of the upper frame as well as an extension part  430  of a lower frame. Spacer blocks  415  and  416  can be arranged in the extension part of the upper frame and the lower frame. The parts of the outer frame  400  protect the device  100 ,  200  in accordance with the invention and the extension part  420  of the upper frame also protects the device when the device is not in use. The extension part  430  of the lower frame also protects and surrounds the device. The spacer blocks  415  and  416  possibly arranged between the extension part  420  of the upper frame and the extension part  430  of the lower frame are removed when the device and/or separate jacks  405 ,  406  lift the parts  420 ,  430  apart from each other. The jack parts  405 ,  406  can be placed in connection with the device, when needed, for example, in a situation when the lifting distance of the device  100 ,  200  itself is not sufficient. In addition, in connection with the device it is possible to arrange a cleaning device  425  for the fabric to be pulled in, for example, at least one of the surfaces of the fabric is cleaned using a pneumatic or hydraulic means such that fabric-damaging particles cannot enter the feed-in nip. The use of this kind of cleaning device  425  is very advantageous, for example, when the device is used for feeding in a wire, in which connection even a small dry particle might make a hole in a thin wire. In connection with the device it is also possible to arrange a cleaning device, for example, a doctor or equivalent, for its bands. A door can also be arranged at the front side of the outer frame  400 , which is indicated by the arrow  435 , thereby enabling the structure to be closed completely from contamination splashing from the surroundings. When equipped with the outer frame  400  illustrated in the figure, comprising the upper frame extension part  420  and the lower frame extension part  430 , the device can be replaced when fabrics are not being pushed into the machine because the frames and their extension parts carry the load. In that connection, it is advantageous to arrange, for example, rails in connection with the extension part of the lower or upper frame of the outer frame to replace the device. The rails can be, for example, of telescopic construction. 
     The operation of the device is described next. In the rest position, the units  100 ,  200  are in the load-bearing beam R of the tending side HP one on top of the other such that the load carried by the load-bearing beam R is transmitted to support points of the vertical frames R only through the side frames  101 ,  102  of the units or through the frames surrounding the device. The bands  130  of the units are not subjected to any load. When the pressure chamber inside the lower unit  100  and the pressure chamber inside the upper unit  200  are pressurized, the load is transferred from the side frames of the units to the pressure chambers and to the bands. The side frames are separated from each other to the extent that there is room for a fabric to pass between them, and the pressure medium between the pressure chamber and the band carries the load. Between the units, the band is subjected only to the friction caused by the pressure medium, said pressure being very small. The fabric can now be pushed into the throat between the bands, wherefrom it is transferred between the bands through the device. A drive motor is coupled to at least one roller of one band for pulling the band and, with it, the fabric through the device. When the fabric is pushed into the throat between the bands, a suitable wedge piece can be used ahead of the fabric in order that the fabric may be brought more easily between the bands without the inlet edge of the fabric being damaged. Such a wedge piece can also be used at the trailing edge of the fabric so that the trailing edge of the fabric should not be damaged when the fabric is transferred through the device. 
     In the embodiment shown in  FIGS. 2-3  there is a roller  110 ,  120  at both ends of each unit  100 ,  200  and in the embodiment shown in  FIG. 4  one roller  120  is replaced with a curved slide surface  125 . It may also be contemplated that the rollers at both ends of the unit are replaced with curved slide surfaces. In that case, the fabric is placed between the bands  130  and pulled with the bands  130  to the inner side of the load-bearing beams R on the tending side HP of the machine. The pressure chambers  300  are then pressurized such that the side frames  101 ,  102  of the device are separated from each other, and the pressure medium of the pressure chambers  300  and the bands  130  carry the load. The pulling of the fabric placed between the bands through the device can then be accomplished using conventional means, for example, a block and tackle or a winch. 
     The band  130  is advantageously made of metal, such as steel, but a polymer fiber band can also be used. A liquid, such as water or oil, can be advantageously used as the pressure medium of the pressure chamber  300 , but gas is also possible. 
     The seal holders  330 ,  340  are also advantageously formed of metal. 
     Because of the rectangular groove  301 , the pressure area of the pressure chamber  300  can be made to match the area of the rectangular band  130  well, but any other polyhedron-, circle- or oval-shaped groove  301  is also possible. There can also be several chambers although it is more advantageous to accomplish one chamber. 
     The material of the first seal  310  is advantageously rubber and the material of the second seal  320  is advantageously graphite. 
     Above, the invention has been described in connection with a press section, which is one advantageous site of application of the invention. However, the invention can be applied in all web-forming equipment having changeable fabrics. 
     The various details of the invention may vary within the inventive idea defined by the claims set forth below and differ from those given above by way of example only.