Abstract:
A frame for a twin-wire press is disclosed including pairs of side members including upper and lower side members arranged on opposite sides of the press, between which upper and lower rolls are attached, a plurality of transverse beams arranged between the pairs of side members which themselves are sections of flat sheet metal and spacers for mutually releasably connecting the side members with the sheet metal being formed so that it permits a degree of curing in the vertical plane to facilitate access to the space between the upper and lower rolls. A method for exchanging wire in a twin-wire press of this type is also disclosed.

Description:
This application is a 371 of PCT/SE05/00850 filed on 3 Jun. 2005. 
   FIELD OF THE INVENTION 
   The present invention relates to a frame for a twin-wire press and a method for exchange of wire in twin-wire press comprising said frame. 
   BACKGROUND OF THE INVENTION 
   Twin-wire presses for dewatering of a fiber suspension and forming of a continuous web thereof are previously known. Dewatering of the pulp is usually done from an inlet pulp concentration of 3 to 8 percent by weight to an outlet pulp concentration of 30 to 50 percent by weight. According to the state of the art, such twin-wire presses comprises lower rolls, an endless lower wire running in a path around the lower rolls, upper rolls, and an endless upper wire running in a path around the upper rolls. The two wires co-operate with each other along sections of said paths that run substantially in parallel with each other for dewatering of the fiber suspension between the wires during displacement thereof. An inlet box provides for supply of the fiber suspension to a wedge-shaped dewatering space between the wires. The twin-wire press further comprises two dewatering tables supporting the respective wire in said sections of the path and forming the wedge-shaped dewatering space between the wires for initially pressing and dewatering the fiber suspension, whereby a web is formed between the wires, and a roll arrangement situated after the dewatering tables in said sections of the paths, as seen in the direction of movement of the wires, for finally pressing and dewatering the web between the wires, so that the web will get a desired dryness. 
   It is often necessary in a simple way and as quickly as possible during maintenance, exchange of wire and cleaning of the twin-wire press, without prolonged stoppage of production, to be able to reach the space between the upper and lower rolls in the roll arrangement. The supporting structure of known twin-wire presses is formed of a framework of longitudinal, parallel arranged, I-beams in the longitudinal direction of the twin-wire press, respectively of transversely parallel arranged I-beams in the transverse direction of the twin-wire press. The transverse and longitudinal beams are firmly fixed, such as welded together, with each other whereby a rigid and stable framework structure is formed. The rolls in these presses are arranged in connection to the longitudinal beams between opposite long sides of the press. In order to be able to reach the space between the upper and lower rolls of the known presses, a hinge joint is arranged along a long side of the press between two longitudinal parallel arranged beams, hereinafter called first longitudinal side member. A space in the longitudinal direction of the press between upper and lower rolls on the opposite long side of the press may then if required be widened by disengaging fixations in the shape of distance elements between longitudinal parallel arranged beams on this opposite side, hereinafter called second longitudinal side member. With the aid of a jack, or the like, arranged to push apart two of the parallel arranged second longitudinal side members between which distance elements have been disengaged, a space between upper and lower rolls can be widen, whereby it is possible to reach the space in the roll arrangement for maintenance, cleaning and exchange of wire. 
   However, this known structure with a hinge joint is very expensive, complicated and not flexible. Even during production of the twin-wire press a decision has to be taken on which longitudinal side of the press the hinge joint shall be arranged, since that is a question of vital importance for the accessibility to said space between the rolls once the twin-wire press is arranged on the intended position in the paper plant. 
   One object of the present invention is to achieve an easier, more effective and improved twin-wire press where the space between the upper and lower rolls in the roll arrangement is easily accessible for maintenance, exchange of wire and cleaning if required, and where at least those drawbacks that are associated with previously known state of the art can be partially eliminated. It is another object of the present invention to achieve a twin-wire press that permits an option which long side of the press the space shall be widen between upper and lower rolls for accessibility for maintenance, exchange of wire and cleaning. Yet another object of the present invention is to provide a twin-wire press where maintenance, exchange of wire and cleaning of the press can be carried out cost efficiently and in a work saving way. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, these and other objects have now been realized by the invention of a frame for a twin-wire press comprising first and second pairs of longitudinal side members, the respective pairs of longitudinal side members comprising an upper side member and a lower side member arranged along each opposite longitudinal side of the twin-wire press, between which first and second pairs of upper and lower rolls are intended to be attached in the twin-wire press, and a plurality of transverse beams arranged between the first and second pairs of longitudinal side members, the respective pairs of the upper and lower side members at least partially comprising sections of flat sheet metal elements, and distance elements for mutually releasably connecting the upper and lower side members, the sheet metal elements being formed such that they permit a predetermined degree of curving in the vertical plane transverse to the horizontal plane which facilitates access to the space between the upper and lower rolls for performing maintenance, exchange of wire or cleaning. In a preferred embodiment of the frame of the present invention, respective pairs of the side members comprise recesses intended for fastening rolls between the first and second pairs of side members. 
   In accordance with another embodiment of the frame of the present invention, the lower side members comprise a substantially flat sheet metal element. 
   In accordance with another embodiment of the frame of the present invention, the upper side members comprise a substantially flat sheet metal element. 
   In accordance with the present invention, a method has also been discovered for the exchange of wire in a twin-wire press including a frame as set forth above in which an endless lower wire runs in a path around the pair of lower rolls and an endless upper wire runs in a path around the pair of upper rolls, the method comprising disengaging the distance elements from the upper and lower side members of one of the pair of side members, pushing apart the upper and lower side members of the one of the pairs of side members by causing the sheet metal element of the other of the pairs of side members to curve to some extent in a vertical plane transverse to the horizontal plane under which the upper and lower side members of the one of the pairs of side members are pushed apart, removing the distance elements to form a free opening between the upper and lower side members of the one of the pair of side members and removing the at least one of the lower and upper wires through the free opening between the upper and lower side members of the one of the second pairs of side members. Preferably, the sheet metal elements of the one of the pairs of side members are curved by means of at least a press apparatus. 
   These objects are thus achieved with a frame for a twin-wire press according to the present invention. The frame comprises a first and a second pair of longitudinal side members. The respective pairs of side members comprises an upper side member and a lower side member and are arranged along each opposite longitudinal long side of the twin-wire press, between which first and second pair of side members rolls are arranged to be attached in the twin-wire press. Furthermore, the frame comprises several transverse beams arranged between the first and the second pair of opposite side members. The frame includes respective side members that at least partially comprise sections of flat sheet metal elements. Upper and lower side members of the respective pairs of side members are mutually releasably connected by distance elements. The sheet metal element is formed such that it permits a certain extent of curving in a vertical plane, transverse to the horizontal plane, which facilitate accessibility to the space between the upper and lower rolls for performing work with maintenance, exchange of wire and cleaning. 
   In view of the fact that the longitudinal side members of the frame partially comprise flat sheet metal elements, the requirement of a hinge structure that is necessary in conventional twin-wire presses can be completely eliminated. In order to reach the space between upper and lower rolls along a long side of the press, the sheet metals&#39; own curvature is utilized. By curving the sheet metal of the side members on one of the longitudinal sides of the press, and disengaging the distance elements between the opposite longitudinal side members on the second long side of the press, the upper and lower side members can be brought apart to facilitate access to the space between the upper and lower rolls. The present invention facilitates that work with maintenance, exchange of wire and cleaning of the twin-wire press can be performed efficiently whereby the operation of the press only needs to be interrupted for a shorter period. Thus, a cost saving can be achieved thanks to a shorter time for interruption and an elimination of the conventional hinge structure. Furthermore, the present invention also means that the production and the assembly of the twin-wire press becomes more effective, since apertures of the sheet metal elements of the side members can be cut out already at the production which results in that there will be no matching difficulties at the assembly. Besides, the flat sheet metal elements of the side members can form attachments for assembly of the bearing housing of the rolls, which results in a simplified assembly. Another advantage is that all apertures that are needed in the sheet metal elements can be machined directly in the sheet metal at the production that leads to that there will be exact positions for fastening of rolls and other details. 
   The present invention also relates to a method for exchange of wire in a twin-wire press comprising a frame as described above, where upper and lower rolls are arranged between the first and second pair of side members. Furthermore, the twin-wire press comprises an endless lower wire running in a path around the lower rolls, and an endless upper wire running in a path around the upper rolls. According to the method of the present invention, the fixation of the distance elements in attachments to the upper and lower side member of the second pair of side members is disengaged; the upper and lower side member of the second pair of side members are pushed apart, by causing the sheet metal elements of the first pair of side members to some extent to curve in a vertical plane, transverse to the horizontal plane, under which the upper and lower side members of the second pair of side members are pushed apart; the distance elements are removed, whereby a free opening is formed between the upper and lower side members of the second pair of side members; and the lower and/or the upper wire is removed through the free opening between the said upper and lower side members of the second pair of side members. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Additional preferred embodiments according to the present invention are evident from the following detailed description with reference to the accompanying drawings, wherein: 
       FIG. 1  is a side, elevational, schematic, cross-sectional view through a twin-wire press according to one embodiment of the present invention; 
       FIG. 2  is a side, perspective, schematic, view of a frame for a twin-wire press according to one embodiment of the present invention; and 
       FIG. 3  is a front, partial, perspective, schematic view of a fastening of a bearing housing of rolls in a frame according to  FIG. 2 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a twin-wire press  2  according to the present invention. The twin-wire press  2  comprises three lower rolls, namely, a drive roll  4 , a control roll  6  and a tensioning roll  8 . An endless lower wire  10  runs in a path around the lower rolls,  4 ,  6  and  8 . In a corresponding manner an upper endless wire  12  runs in a path around three upper rolls, namely, a drive roll  14 , a control roll  16  and a tensioning roll  18 . An upper dewatering table  20 , that supports the upper wire  12 , and a lower dewatering table  22 , that supports the lower wire  10 , forms the dewatering space  24  between the wires,  10  and  12 , in which the fiber suspension/web M is dewatered. “Press section” refers to an ordinary roll arrangement according to the state of the art that can involve a plurality of roll pairs  25 , such as schematically shown in  FIG. 1 . An inlet box  26  is arranged at one end of the press. 
     FIG. 2  shows a frame for a twin-wire press described with reference to  FIG. 1 , mainly intended as a frame for the roll arrangement of the press. The frame comprises a first and a second pair of longitudinal side members,  32  and  34 . The first pair of side members  32  comprises an upper side member  32 ′ and a lower side member  32 ″ arranged along a longitudinal first long side of the twin-wire press. The second pair of side members  34  comprises an upper side member  34 ′ and a lower side member  34 ″ arranged along a longitudinal second long side of the twin-wire press. Between the first  32  and second  34  pair of side members in the twin-wire press are rolls intended to be attached. Furthermore, the frame comprises several firmly fastened transverse beams  36  arranged between the first and second pairs of opposite side members,  32  and  34 . 
   The respective side members,  32 ′,  32 ″,  34 ′, and  34 ″, comprise at least partial sections of flat sheet metal elements. Upper and lower side members,  32 ′ and  32 ″, of the first pair of side members  32 , and respective upper  34 ′ and lower side member  34 ″ of the second pair of side members  34 , are mutually releasably connected by distance elements  38  (in  FIG. 2  are the distance elements of the second pair of side members  34  are removed). 
   The respective side members,  32 ′,  32 ″,  34 ′, and  34 ″, comprise recesses  40  intended for fastening of rolls between the first and second pair of longitudinal side members,  32  and  34 . As shown in the preferred embodiment of the frame in  FIG. 2 , substantially the whole lower side members,  32 ″πand  34 ″, respectively substantially the whole upper side members  32 ′ and  34 ′, can comprise flat sheet metal elements. However, the whole side members need not be comprised of flat sheet metal elements according to the most general embodiment, but it is sufficient first of all that the side members at least partially comprises sections of flat sheet metal elements. In that respect, at least those sections of the side members that are adjacent to the distance elements suitably comprises flat sheet metal elements. Preferably, those sections of the side members that are adjacent to the fastening of the rolls to the side members can comprise flat sheet metal elements. The sheet metal elements, and thus the sections of the side members that comprises sheet metal elements, are formed such that, to certain extent, they permit a curving in a vertical plane V, transverse to the horizontal plane H. 
   At the time of an exchange of wire in a twin-wire press  2  (see  FIG. 1 ) comprising the frame according to  FIG. 2 , which press comprises upper and lower rolls (see  FIG. 1 ;  25 ′,  25 ″) and an upper and lower wire ( FIG. 1 ), the following stages are performed in the given sequence: 1) The fixation of the distance elements  38  in attachments  42  to the upper  34 ′ and lower  34 ″ side member of the second pair of side members  34  are disengaged by removing those screws by which the distance elements are fixed to the attachment  42 . 2) The upper  34 ′ and lower  34 ′, side member of the second pair of side members  34  are pushed apart. The upper side member  34 ′ is transferred in a direction away from the lower side member  34 ″ of the second pair of side members by causing the sheet metal elements of the first pair of side members  32  to curve to some extent in a vertical plane V, transverse to the horizontal plane H under which the upper  34 ′ and lower  34 ″ side member of the second pair of side members are pushed apart. For this purpose a press apparatus is suitably arranged between transverse beams that are adjacent to the first pair of side members. The sheet metal elements of the first pair of side members  32  are curved by means of the press apparatus whereby consequently the upper  34 ′ and lower  34 ″ side member of the second pair of side members  34  is pushed apart in order to be able to disengage the distance elements. 3) The distance elements  38  are removed, whereby a free opening  43  is formed between the upper  34 ′ and lower  34 ″ side members of the second pair  34  of side members.  FIG. 2  shows the frame after the distance elements at the second pair of side members have been removed. 4) Possibly the upper  34 ′ and lower  34 ″ side member of the second pair of side members  34  are brought further apart in order to create a larger free opening  43 . The lower and/or the upper wire are removed through the free opening  43  between the said upper  34 ′ and lower  34 ″ side members of the second pair  34  of side members. 
   With reference to  FIG. 3 , fastening of a lower roll  44  and an upper roll  46  to a flat section of a sheet metal element of the upper and lower side members,  32 ′ and  32 ″, respectively, of the first pair of side members  32  in  FIG. 2 , is shown according to a preferred embodiment. By means of attachments  48  such as pins, bolts or the similar, a projecting section  50  of a bearing housing  52  of the lower roll  44  is fixed to the flat sheet metal element section  54  of the lower side member  32 ″. In  FIG. 3  is also shown the fastening of a hydraulic cylinder  56  between a flat sheet metal element section  58  of the upper side member  32 ′ and a projecting section  60  at a bearing housing  62  of the upper roll  46 . By this arrangement of the bearing housing  52 ,  62  of the rolls to the frame according to the present invention, a more effective and uncomplicated fastening of the rolls is achieved in comparison to what has been possible in the conventional existing frameworks in the previously known twin-wire presses. 
   Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.