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.

Twin-wire presses for dewatering of a fibre suspension and forming of a continuous web thereof are previously known. Dewatering of the pulp is usually done from an inlet pulp concentration of 3-8 percentages by weight to an outlet pulp concentration of 30-50 percentages 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 fibre suspension between the wires during displacement thereof. An inlet box provides for supply of the fibre 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 fibre 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 at 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 w'hereby 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 widen by disengaging fixations in the shape of distance elements between longitudinal parallel arranged beams on this opposite side, hereinafter called second longitudinal side member. By the. aid of -a jack, or the similar, 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 at 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.

The 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. Further is an object 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 an object 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.

These objects are 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. Further the frame comprises several transverse beams arranged between the first and the second pair of opposite side members. The frame is characterised in that respective side member at least partially comprises sections of flat sheet metal elements. Upper and lower side members of the respective pairs of side members are mutually releasable connected by distance elements. Said sheet metal element is formed such that it permits a certain extent of curving in a vertical plane, transverse 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.

Thanks to the fact that the longitudinal side members of the frame partially comprises 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 own curvature is utilized. By curving the sheet metal of the side members on one of the longitudinal side of 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 and facilitate access to the space between 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 ' need 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. Yet an 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 according to claim 1, where upper and "" lower "rolls are arranged between the first and second pair of side members. Further 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. The method is characterised in that: 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 bringing said sheet metal elements of the first pair of side members to in some extent curve . in a vertical plane, transverse the horizontal plane, under which the upper and lower side member 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.

Additional preferred embodiments according to the present invention are evident from the following by the detailed description with reference to the accompanying drawings. The present invention will now be described in more detail by embodiments, with reference to accompanying drawings, without restricted interpretation of the invention thereof, where

fig. 1 schematically shows in an overview a longitudinal cross-section through a twin-wire press according to an embodiment of the present invention.

fig. 2 'schematically shows in an overview, a frame" for' a" twin-wire press according to an embodiment of the present invention, and

fig. 3 shows schematically a fastening of a bearing housing of rolls in a .frame according to fig. 2.

Fig. 1 shows a twin-wire press 2 according to the present invention. The twin-wire press 2 comprises three lower rolls, viz. 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, viz. 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, 12 in which the fibre 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 frame for the roll arrangement of the press. The frame comprises a first and a second pair of longitudinal side members 32, 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 said first 32 and second 34 pair of side members in the twin-wire press are rolls intended to be attached. Further the frame comprises several firmly fastened transverse beams 36 arranged between the first and the second pair of opposite side members 32, 34. The respective side members 32', 32'', 34', 34'' comprises at least partially sections of flat sheet metal elements. Upper and lower side members 32', 32' ' of the . first pair of side members 32, respective upper 34' and lower side member 34'' of the second pair of side members 34, are mutually releasable connected by distance elements 38 (in fig. 2 are the distance elements of the second pair of side members 34 removed) .

The respective side members 32', 32'', 34', 34'' comprises recesses 40 intended for .fastening of 'rolls between the first and second- pair of longitudinal side members 32," 34.. As shown in the preferred embodiment of the frame in fig. 2, substantially the whole lower side members 32'', 34'', respectively substantially the whole upper side members 32', 34', can comprise flat sheet metal elements. However, the whole side members need not to be comprised of flat sheet metal elements according to the most general embodiment, but it is sufficient first of all that the o

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. Said sheet metal elements, and thus the sections of the side members that comprises sheet metal elements, are formed such that they" to "certain extent permit" a curving in""a vertical plane V, transverse the horizontal plane H.

At the time of an exchange of wire in a twin-wire press 2 (see fig. 1) comprising said 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) , 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 in 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 direction away from the lower side member 34''- of the second pair of side members by bringing said sheet metal elements of the first pair of side members 32 to curve for some extent in a vertical plane V, transverse 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 is suitably a press apparatus arranged between transverse beams that are adjacent to the first pair of side members. Said 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 cause 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, a 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 a 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.