Suction boxes are used in connection with formers, a pulp web being arranged to run between wires over the suction zone of the suction box. The run of the web is made curved in a desired manner by means of different curved blade-shoe shapes, in which connection the removal of water can be affected not only by fabric tension but also by centrifugal force and suction. The state-of-the-art suction boxes use stationary foil blades, so that there is a vacuum between the foils.

Stationary foil blades wear wires through friction and the foil blades also wear for this reason. The friction also increases the drive power needed for moving the wires. When a combination of a loading element and a suction box is used, the wear of wires and the drive power become still greater.

This patent application proposes using a meandering path for a pulp web to enhance dewatering. In particular, it is an object to form a dewatering unit in a twin-wire area, in which connection dewatering pressure is formed by fabric tension and centrifugal force. The effect of both of the above-noted forces increases with increasing machine speeds.

The patent application proposes using in dewatering not only the vacuum of the suction box but also the adjustable curvature of the web path. By adjustment of the curvature of the web path it is possible to affect not only fabric tension but also the centrifugal force acting on the web and, thus, the removal of water from the pulp web.

In accordance with the invention, dewatering is arranged to take place specifically at a suction box such that the suction box used is of a kind in which, between

blade shoes or fabric guide elements, second guide elements are arranged to act on the other side of the web, which second guide elements can be loaded and moved in accordance with the invention. Advantageously, the guide elements used are also guide elements which are rollers or equivalent and thus arranged to rotate and to reduce friction. In that connection, wear of wires is substantially reduced and the drive power required for rotating the wires decreases. The rollers may be advantageously mounted by bearings hydrodynamically, electrically or magnetically. In accordance with the invention, the second guide elements which can be loaded and adjusted in position are located between the first guide elements. In that connection, dewatering can be controlled over the length of the suction box by affecting the guide elements and, thus, the run path of the web, thus making it a meandering path. The guide elements produce pulsating dewatering of the web, which is enhanced by the vacuum of the suction box. The fines distribution in the web can be effectively influenced by means of the magnitude of the vacuum.

The dewatering device of the invention in a paper machine or equivalent is characterized by the disclosure in the claims.

In the following, the invention will be described with reference to some advantageous embodiments of the invention illustrated in the figures of the appended drawings, but the invention is not meant to be exclusively confined to these embodiments.

Figure 1A illustrates a former in accordance with the invention, which former comprises loaded second guide elements in accordance with the invention, by means of which elements the web is caused to run along a meandering path at a suction box.

Figure 1B shows loading elements of second fabric guide elements, which loading elements comprise cylinder devices in this embodiment. The former type is

different from that of the embodiment of Fig. 1A. Stock is supplied onto a wire Ha and only after that is a pulp web W passed into a gap between wires Hl and H2.

Figure 1C shows the area A2 from Fig. 1B on an enlarged scale.

Figure 2 illustrates a meandering path of the pulp web W produced by means of the device arrangement in accordance with the invention. The illustration is an enlargement of the area Al in Fig. 1A.

Figure 3 shows one advantageous position for a dewatering device in accordance with the invention in a former of a third type.

Figure 4 shows a dewatering device in accordance with the invention in a hybrid former.

Fig. 1A shows an embodiment of the invention in a former 100, in which the former comprises forming wires Hl and H2 and a dewatering device 10 in accordance with the invention. Stock is introduced into a gap between the wires Hl and H2 as shown by the arrow Fi. As shown in Fig. 1A, the former 100 comprises a wire loop formed by the upper forming wire Hl, and wire guide rolls Eel, Ee2, E3, as well as a dewatering roll E4. Similarly, the second forming wire H2 forms a wire loop and comprises inside it wire guide rolls Di, D2, D3 and D4, as well as a roll D5 on the outside. Inside the wire loop formed by the wire H2 there is a suction box 110. The dewatering device 10 comprises a suction box 11 inside the wire loop of the first wire Hl. The suction box 11 comprises in its connection compartments SI, S2, S3 and S4, the vacuum of which can be regulated, in which connection between the compartments there are fabric guide elements 12al, 12a2, 12a3,12a4 and 12a5, advantageously rollers 12al, 12a2... mounted rotatably in bearings. The rollers 12al, 12a2... are preferably mounted by means of bearings to rotate in roller cradles 13al, 13a2..., and the bearing arrangement is advantageously hydrodynamic. The equipment comprises inside the wire loop of

the second wire H2 second fabric guide elements 14al, 14a2,14a3 and 14a4, advantageously loaded elements comprising second backing parts, advantageously rollers 15al, 15a2,15a3,15a4 arranged to rotate and mounted in bearings. The rollers 15al, 15a2... are so grouped that, for example, the roller 15al is located in the middle of the distance between the guide elements 12al, 12a2. The roller 15a2 is located in the middle of the distance between the guide elements 12a2 and 12a3, etc. By means of said second loading elements 14al, 14a2..., the wires Hl, H2 and the pulp web W conveyed between them are pressed towards the suction box 11, thereby causing the run of the web W to meander and thus to become curved and, in the dewatering of the pulp web, it is possible to utilize the centrifugal force acting on the pulp web in the curved runs of the web.

Fig. 1B shows a dewatering device in accordance with the invention in connection with another type of former 200. Fig. 1C shows an enlargement of the area A2 from Fig. 1B.

Figs. 1B and 1C show a dewatering device of second guide elements 14al, 14a2... in connection with the former type 200, in which stock is passed, as shown by the arrow Fl, onto a lower forming wire H2 and a pulp web W is passed with the forming wire H2 into a gap between the wires H2 and Hl. The guide rolls of the wire H1 are designated by El, E2 and E3. A suction box 11 is similar to that of the embodiment shown in Fig. 1A and so is the structure of the second fabric guide elementsl4a1, 14a2... in accordance with the invention. Loading elements 16al, 16a2... of the second fabric guide elements 14al, 14a2... are described in greater detail based on Figs. 1B and 1C. In the former 200 of Figs. 1B and 1C, the wire H2 is guided over guide rolls D1, D2, D3, D4 and D5, which guide rolls are located inside the wire loop of the forming wire H2, a second suction box 110 being also located inside the wire loop. The arrow Fi designates the location where stock is passed onto the wire H2.

Figs. 1B, 1C show an embodiment of the invention in which the second guide elements 14al, 14a2... comprise the loading devices 16al, 16a2... In this embodiment, the loading devices 16al, 16a2... are formed of cylinder devices, each cylinder device comprising a cylinder frame 17 and a cylinder arm 18 disposed inside it as well as a piston 19 in it. Attached to the cylinder arm 18 is a cradle 20 in which, for example, a guide element 15al, such as a roller, is arranged to rotate. The bearing arrangement between the guide element 15al and the cradle 20 is hydrodynamic. A similar arrangement is provided in the case of the second fabric guide element 15a2. By operating the loading devices 16al, 16a2..., the fabric guide elements 14al, 14a2... can be loaded and moved towards and away from the wires/web Hl, W, H2. Thus, by operating the loading devices 16al, 16a2..., the pulp web W can be pressed, as desired, towards compartments S1 and S2 in the suction box 11. By this means, the run of the fabrics, such as the wires H1 and H2, the pulp web W can be made curved in a desired manner, and dewatering can be controlled over the entire length of the suction box 11 by affecting the curvature of the wires/web HI, W, H2 and the tension of the wires H and H2.

The loading devices 16al, 16a2..., when comprising cylinder devices, can be, for example, pneumatically operated.

Fig. 2 shows the area A from Fig. 1A on an enlarged scale. The pulp web W and the wires H1 and H2 run along a meandering path. The pulp web W runs between the wires H1 and H2 along a meandering path. By this means, centrifugal force can be directed at the pulp web W as desired and so can desired dewatering and also the desired tension of the wires Hl and H2.

By a paper machine or equivalent is also meant board, soft tissue and pulp drying machines.

Fig. 3 shows one arrangement in accordance with the invention in a former 300, in which stock is sprayed, as shown by the arrow Fl, between wires Hl and H2 in the area of a dewatering roll E4, which is followed by a curved blade shoe Pi. Water is removed from the pulp web W by means of the curved blade shoe Pi, and the blade shoe Pi is followed by a dewatering device 10 in accordance with the invention for increasing the solids content of the web.

Fig. 4 shows one arrangement in accordance with the invention in a hybrid former 400, in which in a twin wire zone there is a combination P2 of a loading element and a suction box, by means of which water is removed from the pulp web W and the properties of the web are affected. After this there is a dewatering device 10 in accordance with the invention for increasing the solids content of the pulp web W before it is transferred to a press section.