Gap former structures in which stock is passed from a headbox to a gap between forming wires and further along between the forming wires are known from prior art. In the apparatus arrangement according to prior art, in the vicinity of the gap, rotating suction rolls i. e. forming rolls or sets of stationary dewatering blades have been used in water removal and wire control.

A disadvantage related to prior art former arrangements is, for example, the large diameters required by the roll arrangements, which also results in a great machine length and width and thus in high machine manufacturing costs. In addition, the headbox slice structures have to be made on the terms of the diameters of the rolls to make sure that the distance of the free slice jet from the headbox to between the wires does not become too long. Friction occurs between the wires and the sta- tionary dewatering elements, which friction further causes wear of the wires.

What is more, the forming rolls are expensive and always require a spare roll.

In this application, instead of a forming roll, a forming box is used in the gap for- mer right where a gap K closes, which forming box comprises rollers rotatably mounted by means of bearings and disposed against the wire.

By using, according to the invention, a forming box comprising rollers arranged to rotate, a good water removal pressure is obtained in the web. Using rollers makes the friction between the wire and the dewatering elements associated with it smaller. This way greater wire tensions can be achieved, which further improves the efficiency of water removal. There is very little wear of wires. By making the

web run in a curved manner in connection with the forming box, uniform water removal from the stock web through both forming wires can be achieved, due to centrifugal force.

Furthermore, by using a low forming box according to the invention the height of the box remains low and, as a result, a smaller height and length of the former can be provided compared to conventional arrangements. Consequently, the construc- tion investment costs and the material costs for the entire machine become lower.

Using a forming box according to the invention helps to make the drainage routes of water from the stock short, and thus a good forming result is obtained.

By using a forming box according to the invention instead of conventional dewa- tering rolls the structure of the headbox is also affected so that the cone of the headbox can be made blunter. This makes the length of the machine shorter. By thus providing a shorter wire forming section it is possible to reduce the structural costs compared to prior art formers.

The apparatus in the forming of a web in a paper machine or the like according to the invention is characterized in what is presented in the claims.

The invention will now be described with reference to some preferred embodi- ments illustrated in the figures of the accompanying drawings, to which embodi- ments the invention is, however, not intended to be solely confined.

Figure 1A shows a first preferred embodiment of the invention i. e. a so-called vertical gap former.

Figure 1B is a separate side view of the forming box according to the invention related to the apparatus of Figure 1A.

Figure 1C shows the forming box according to Figure 1B, seen in the direction of the arrow Kl of Figure 1B. No wire runs and no web run between the wires are shown in connection with Figures 1B and 1C.

Figure 2 shows a second embodiment of the apparatus according to the invention i. e. a so-called horizontal gap former.

Figure 3 is a cross-sectional view of the forming box according to the embodi- ment of Figure 2 at the end bearings of the rods.

Figure 1A shows an apparatus 100 according to the invention in the forming of a web in a paper machine or the like. Figure 1A shows a so-called vertical former type, in which a stock suspension W is passed from a headbox 10 to a gap K be- tween a first forming wire 11 and a second forming wire 12. The first wire 11 has the shape of a wire loop, inside which loop there are wire guide rolls 13al, 13a2, 13a3,13a4 and 13a5. The second wire loop 12 comprises, inside the wire loop, wire guide rolls 12al, 12a2,12a3 and 12a4. The apparatus 100 according to the invention, which is a gap former, comprises, according to the invention, a forming box 15, according to the invention, as a first dewatering element (when seen in the running direction Li of the web) in the area where the wires 11 and 12 meet. The forming roll has thus, according to the invention, been replaced by the forming box 15. The forming box 15 comprises rotating rollers or rods 16al, 16a2,16a3, 16a4,16a5 and 16a6. Inside a frame 200 of the forming box 15 there is a suction space DI, in which an underpressure of the order of 1 kPa-40 kPa is generated.

The rollers 16au... 16a6 are disposed in the frame 200 of the suction box such that, at the rollers, the wire loop runs in a curved manner. The centre of the radius of curvature is located inside the wire loop of the forming wire 11. Most advanta- geously, there is only one radius of curvature, which is advantageously in the range of 500 mm-2000 mm. Several radii of curvature may also be used. The curvature at the forming box 15 is then advantageously formed such that there is,

in the running direction Li of the wire loop, first a curvature portion RI, which is greater than a following curvature portion R2 of the forming box. The length Al of the forming box 15 is 100 mm-1000 mm, advantageously 100 mm-400 mm.

The radius of curvature Rl is advantageously in the range of 1000 mm-2000 mm and the radius of curvature R2 is advantageously in the range of 500 mm-1500 mm.

The water drains out of the stock web W at the forming box 15 from inside the forming wires 11 and 12 towards the suction box 15 and also, due to wire tension and centrifugal force, outwards in the opposite direction. This way, the drainage of water from the stock web W can be made to take place in two directions and a stock web W of uniform quality can be provided. The forming box 15 can also be divided, in the longitudinal direction, into compartments each of which can be separately provided with the necessary underpressure.

A suction box 17 is located after the forming box 15 and in the running direction Li of the web and wires inside the wire loop of the second forming wire 12, which suction box comprises blades 18al, 18a2, 18a3 and 18a4, and water from the stock web is passed between these blades to an underpressurised suction space Dz inside the suction box 17. Loading elements are shown in the figure with reference num- bers 19ai, 19a2... 19a4, which loading elements have, from inside the wire loop of the forming wire 11, such an effect in the area of the suction box 17 that said load- ing elements load the web and wire runs between the blades 18al, 18a2,18a3, 18a4. The loading elements 19ai, 19a2... may be, for example, pneumatic cylin- ders loadable with compressed air.

As shown in the figure, a suction roll 12a2 is located inside the wire loop of the second forming wire 12 after the suction box 17 (when seen in the direction of the arrow Ll). The suction roll 12al comprises inner suction boxes 20al, 20a2, inside of which there are suction spaces D3 and D4. A different underpressure is effective in the space D3 than in the space D4. By means of the underpressure created in the

space D4 the stock web is kept in contact with the wire 12 and the web W is made to run only in connection with the wire 12 and, as shown by the arrow L2, further in connection with a transfer suction roll 21 of a press section P, by means of the underpressure of an underpressurized space D5 of which suction box suction is applied to the web W and the web W is moved to the press section P, as shown in Figure 1A. The suction roll 12a2 and the suction roll 21 are thus transfer suction rolls. They thus comprise an inner suction box and, in the roll shell, a perforation, via which suction is applied through the wire 12 to the web run W.

Figure 1B is an end view of the forming box 15 and Figure 1C is a view of the forming box 15 seen in the direction of the arrow Kl of Figure 1B. The forming box 15 extends across the width of the wire 11,12. Support parts, preferably ribs 16du, 16d2... 16d6, extending in the running direction Ll of the wire, are disposed on transverse edges Jl, J2 of the forming box. The ribs 16d 16d2... are located under- neath rollers, rods 16al, 16a2... supporting them and preventing them from bend- ing.

Figure 2 shows a second embodiment of the invention, in which an apparatus 100 is composed of a so-called horizontal gap former. In this embodiment, too, a first wire loop 11 comprises wire guide rolls 13al, 13a2, 13a3 and 13a4. The wire guide rolls 13au... 13a4 of the wire loop 11 are located inside the loop-shaped wire loop.

A forming box 15 is located inside said wire loop after a gap K, near the gap K, which forming box is similar to the one disclosed in the previous embodiment.

The forming box 15 comprises rollers, rods 16al, 16a2,16a3 and 16a4, which are rotatably mounted by means of bearings and which are disposed against the wire 11. In this embodiment, too, the rollers, rods 16al, 16a2, 16a3 and 16a4 of the forming box 15 are disposed on a frame 200 of the forming box 15 so that after the gap Kl, with respect to the running direction Ll of the stock web and the wires, there is first a web portion which is determined by the location of the rods and has a radius of curvature RI, the curvature Ri of which web portion is greater than the curvature R2 of the web after it. The curvature Rl is formed by means of

the rollers 16ai, 16a2... for the web run W. The radius of curvature Rl is located on the side the wire loop formed by the forming wire 11 against which the rollers 16al, 16a2 are pressed. The centre of the radius of curvature Ri may advanta- geously be located inside the wire loop against which the rollers 16al, 16a2 are pressed. In this embodiment there is a suction box 17 located inside the wire loop 11, after the forming box 15, the loading elements 19ai, 19a2 and 19a3 of which suction box are, in this embodiment, located inside a wire loop formed by a sec- ond wire 12 and which loading elements apply a force against the wire 12 in the areas between the blades 18al, 18a2 and 18a3. A loading element 19a4 is located before the first blade 18al, seen in the direction Ll. Inside the second wire loop 12 there are wire guide rolls 14al, 14a2, 14a3, 14a4 and 14a5 and outside, in the area between the wire guide rolls 14a4 and 14a5, there is a wire guide roll 14a6. The web W is guided between the wires 11 and 12 to be in connection with a separat- ing suction box 170 located after the guide roll 14a2 (relative to the running direc- tion Li). By means of an underpressure created in the suction box 170, by means of suction applied between blades 180al, 180a2, 180a3 of said suction box 170 underpressure is obtained in the web W and it is kept in contact with the run of the wire 12 and passed to be in connection with a suction roll 21 of a press section P of the web W, which suction roll moves the web W to the press section P to be in connection with a felt H1 of the press section.

By using, according to the invention, a forming box 15 comprising rollers 16al, 16a2... arranged to rotate a good water removal pressure is obtained in the web.

Using the rollers 16al, 16a2... reduces friction between the wire and the water re- moval elements associated with it. This makes it possible to achieve greater wire tensions, which further leads to improved water removal efficiency. There is very little wear of wires. By making the web run in a curved manner in connection with the forming box 15 uniform water removal from the stock web through both wires, the forming wire 11 and the forming wire 12 can be achieved, due to cen- trifugal force.

By using a forming box 15 according to the invention directly in connection with the gap K of the gap former, the height of the box remains low and, as a result, a smaller height and length of the former can be provided compared to conventional arrangements. Consequently, the construction investment costs and the material costs for the entire machine become lower. The drainage routes of water from the stock web become short, and thus a good forming result is obtained.

By using a forming box 15 according to the invention instead of conventional dewatering rolls the structure of the headbox is also affected so that the cone of the headbox can be made blunter. This makes the length of the machine shorter.

By thus providing a shorter wire forming section it is possible to reduce the structural costs compared to prior art formers.

Figure 3 is a cross-sectional view of the forming box 15 according to the inven- tion and according to Figure 2, of the embodiment comprising four rollers 16al, 16a2, 16a3 and 16a4. The rollers or rods 16al, 16a2,16a3 and 16a4, disposed against the run of the wire 11, are mounted hydrodynamically by means of bear- ings in a cradle 160al, 160a2, 160a3, and 160a4. The hydrodynamic substance is preferably water. The cradle 160al comprises pockets 160bl, 160b2, 160b3 in each hydrodynamic zone of the cradle, which pockets further communicate via an in- termediate container space 160d with a line 160cl, which leads further via a pump 50 to a pressure medium container T. The pressure medium is preferably water.

Underpressure is generated in a space Dl by means of a vacuum pump (not shown) and the underpressure is directed at the run of the wire 11 between the rollers 160al, 160a2... and further through the wire 11 at the stock web W. The space D, can comprise compartments Dl', Dol", Du"', each comprising a different underpressure in relation to one another. The underpressure may also be the same in the spaces Dl', Dl'', Dol"'. The cradles 160al, 160a2... may extend across the en- tire length of the rod 16al, 16a2..., as in the embodiment of Figure 2, or they may be located only at each end of the rod 16al, 16a2.

A paper machine or the like refers to paper, board and tissue machines and chemi- cal pulp dryers.