FI76855C - Filtration Press. - Google Patents

Description

76855

FILTERINGSPRESS

The present invention relates to a filter press for removing excess water from a movable pulp cake between two opposite, endless wires, the filter press comprising a pre-press part and a post-press part and interposed wires in a transverse direction extending substantially across the width of the wires. at least during operation of the filter press closer to the wire farther from the turntable than to the center of the turntable.

As the web is formed between the wires, the longitudinal tensile stress of the wire increases at the center of the wire, whereby the tensile stress at the edges of the wire can even be negative, i.e. the wire loosens at the edges, causing sludge to burst from the edges of the wire. To prevent burring, edge seals and "scrapers" are currently used on the straight part of the wire. These have the disadvantage that they wear out quickly as they rub against the wire. For this reason, they often need to be replaced, which is naturally expensive.

It is not possible to increase the speed of the machine and at the same time the speed of the wires if the dry matter content after the pre-pressing section is not high enough. The delimitation of the web is also currently difficult due to the eruption. Thus, there has recently been a need to develop a new type of sealing head for a filter press.

DE patent 181081 discloses a felt roll which is arranged to force the felt strip pulled back into its correct position. In the roll according to the patent, the outer tube is opened at both ends. The opened pieces are equipped with wedge pieces. A wedge ring is arranged between these wedge pieces and the flange. By moving the wedge, the diameter of the tube at both ends can be arbitrarily increased or decreased, and thus the felt can be tightened more or less. DE patent 225082 relates to the uniform tightening of felt machines and wet felts of a paper machine. The publication discloses a conical tensioning roll having a diameter larger at the ends than in the middle, so that the ends of the roll have a higher circumferential speed than in the middle, whereby the felt is subjected to a tension in the width direction of the rolls. DE patent 375749 discloses an apparatus for extending the life of a dewatering felt. For this purpose, before or after the press, two rollers are arranged on a common, rotationally and axially moving bearing on a fixed shaft. In this case, too, the diameter of the roll in the second roll is larger at the ends than in the middle.

The object of the present invention is to provide a filtration press which does not have the aforementioned problems and by means of which the speed of the filter press can be substantially improved. The invention uses a turning roller with a larger diameter at its ends, known from the above-mentioned DE patents 181081, 225082 and 374749, in a new and surprising way to seal the edges of the wires against each other. The filter press according to the invention is characterized in that the turning roller is used to seal the edges of the wires of the filter press against each other so that the sludge cannot escape out of the edges of the wires.

The main advantages of the invention are that since the ends of the turning roll are lower than the center or closer to the wire farther from the turning roll, they cause a higher wire tension on the wire edges than a uniform thick turning roll. The increase in the edge tension of the wire causes the edges to be pressed against the curved portion of the wire against each other, creating a sealing bag at the edges of the wire to prevent sludge from bursting out of the edges of the wire. It has been found empirically that the sealing effect of the turntable according to the invention is particularly strong in the pre-compression part, where the most difficult sealing problems currently occur. In the filter press according to the invention, the delimitation of the web is considerably easier than before.

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In the following, the invention will be explained in detail with reference to the accompanying drawings, in which

Fig. 1 schematically shows a filter press with a pre- and post-press section.

Fig. 2 shows a section of Figs. 1 along line II-II.

Fig. 3 shows fig. 2 correspondingly to another embodiment of the invention during use of the filter press.

Fig. 4 shows fig. 2 correspondingly to a third embodiment of the invention.

Fig. 5 shows fig. 2 in a corresponding manner to another embodiment of the invention.

Figure 1 shows a typical filter press in which a web of slurry mass 3 is formed between two opposing moving wires 1, 2, which is fed between the wires of Figs. 1 seen from the left. The filter press includes a pre-press section 4 and a post-press section 5 to remove excess water from the dough. Between these parts there is a turning roller 6, at which the wires make a bend. In current filter presses, the turntable is completely uniform and rigid. Instead, in the filter press according to the invention, the uniformly thick turning roller has been replaced by the turning rollers 11a 6 according to Figs.

Figure 2 shows a turning roller 6 according to the invention. In it, the diameter of the ends 7 of the turning roller is larger than the diameter of the central part 8 of the turning roller. When making a bend at the turning roller 6, the wires 1, 2 naturally tighten. The cross-section of the lower wire 2 remains straight and the web is formed on it so that the upper wire 1 bends from the center towards the center 8 of the turntable 6. At the ends 7 the wires are together, forming a bag between the wires 1, 2. and from which the wet slurry cannot escape through the edges of the wires.

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The sealing turning roller 6 thus provides the wire 2 with a uniform wire tension over the entire cross section of the wire and thus a cross-sectional shape sealing the edges of the wire between the wires 1, 2 before and after the turning roller and at the turning roller.

Figure 3 shows a turning roller 6, which also achieves the above result in web formation. In it, the ends 7 of the turntable 6 are formed of a harder material than the central part 8 of the turntable. The central part is so soft that it yields and the upper wire forms the arc shown in Fig. 3.

Figure 4 shows a turning roller 6 according to the invention, which is formed of a flexible material. When the filter press is stopped, the turntable is cylindrical and its longitudinal axis is straight, but during use the material gives way so that fig. 4 deflection occurs. Here again, the edges of the wires 1, 2 are tightened together, leaving a bag for the sludge mass between them.

Fig. 5 shows another embodiment, in which again the diameter of the ends of the turning roller 6 is larger than the diameter of the center. In it, the ends 7 and the central part 8 are connected by frustoconical parts 9. This turning roller also provides the sealing effect of the edges of the wires sought in the invention.

It will be clear to a person skilled in the art that the invention is not limited to the exemplary embodiments presented above, but can be varied within the scope of the appended claim.

Claims (1)

5,8855 CLAIMS A filter press for removing excess water from a movable pulp cake (3) between two opposite, endless wires (1, 2), the filter press comprising a pre-press part (4) and a post-press part (5) a turning roller (6) at which the direction of the wires changes and whose turning roller ends (7) are at least during operation of the filter press closer to the wire (2) farther from the turning roller than the center of the turning roller (8), characterized in that the turning roller (6) is used a filter press for sealing the edges of the wires (1, 2) against each other so that the slurry cannot escape from the edges of the wires.