EP0646199B1 - Pressure sorter for fibre suspensions - Google Patents

Abstract

A pressure sorter for the preparation of fibre suspensions obtained from waste paper, with a filter (38) surrounding a rotor (36), a feed chamber (54) between the rotor periphery and the filter and an accepts chamber (58) outside the filter and with section components (86a - 86d) on the peripheral surface of the rotor to generate positive and negative pressure pulses. In order to improve sorting and prolong the useful life of the filter, there is a rotor peripheral area sector in each of the axial sections of the rotor peripheral area acting on the filter between two successive section components in the direction of the rotor periphery, said sector being part of a jacket surface parallel to the feed site of the filter. Measured in the direction of the rotor periphery, the length of each section component is at least approximately the same as that of the next rotor peripheral surface sector, the length of the latter is, however, at least 30 % of the length of the section component in front of it. The section components are designed and arranged at the periphery of the rotor in such a way that, viewed in the direction of the filter axis, the rotor peripheral surface sectors form through channels between the section components along the region of the rotor surrounded by the filter.

Description

The invention relates to a pressure sorter for fiber suspensions, in particular for the preparation of fiber suspensions obtained from waste paper, with a housing in which a stationary sieve, which is rotationally symmetrical to a sieve axis, is arranged, which separates an inlet space encompassed by the sieve from an accept material space located outside the sieve , and with a rotor that can be driven by a motor around the sieve axis, the circumferential surface of which, together with an inlet side of the sieve, delimits the inlet chamber in the radial direction, an inlet communicating with a first axial end of the inlet chamber for the fiber suspension to be treated and one with a second axial end of the inflow space communicating with rejects outlet, profile elements being provided on the peripheral surface of the rotor for generating positive and negative pressure surges in the fiber suspension.

With such pressure sorters there is basically the problem that, if no suitable countermeasures are taken, the throughput of usable fiber suspension through the sieve into the accept material space is drastically reduced by the fact that the sieve openings on the inlet side of the sieve are contaminated by impurities contained in the fiber suspension to be processed, but also through Clumps of fibers are blocked; In addition, such pressure sorters generally tend to the fact that during operation the fibers contained in the fiber suspension to be processed form a nonwoven fabric on the sieve inlet side, by means of which a desired high throughput of usable fibers (long and short) through the sieve openings prevents them from entering the accept material space and also an at least in most cases undesirable fractionation of the fiber suspension is brought about - this is understood to be a division of the amount of fibers contained in the fiber suspension to be processed into shorter and longer fibers, such a nonwoven fabric preventing above all longer fibers from passing through the sieve into the accept material space.

In the prior art, a wide variety of measures can be found by which attempts have been made to master all or part of the problems listed above, it being necessary to bear in mind in this connection that pressure sorters of the type mentioned at the outset are those with their profile elements generated negative pressure surges the screen openings are to be backwashed, ie by generating negative pressure phases in the inlet space, liquid is to be sucked back out of the accept material space through the sieve openings into the inlet space in order to flush out contaminants and fiber aggregates accumulated on the inlet side of the sieve openings from the sieve openings.

A first measure, which can be found in the prior art, is to design the screen openings in such a way that they widen in the passage direction (ie in the direction from the inlet space to the accept material space) (see, for example, US Pat. No. 3,581,903) by the Reduce the risk of clogging of the sieve openings.

In order to both backwash the sieve openings and prevent the formation of a nonwoven fabric on the inlet side of the sieve, another known pressure sorter (see, for example, US Pat. No. 4,276,159) was equipped with a rotor, which has peripheral cleaning blades near the sieve inlet side on average perpendicular to the rotor axis has a wing-like profile for generating positive and negative pressure surges, and its sieve is designed in such a way that a "roughened" sieve inlet side results as a result of sieve openings widened on the inlet side, in order to work through the interaction of the rotating rotor blades with the fiber suspension in the inlet chamber and so on profiled inlet side of the sieve on this and in its vicinity in the fiber suspension to be processed to generate turbulence which counteracts the formation of a nonwoven fabric on the sieve inlet side.

The most varied of proposals for the design of a rotor of a pressure sorter can already be found in the prior art, specifically with regard to the design of the profile elements for generating positive and negative pressure surges in the fiber suspension in the inlet space and / in the accept material space of the pressure sorter. For a long time, the cleaning blades described above, as can be seen, for example, from US Pat. No. 4,276,159, as well as strip-shaped profile elements which run approximately parallel to the sieve axis and are fastened to the peripheral wall of a circular-cylindrical and hollow rotor body, were customary. Examples of such strip-shaped profile elements which are arranged at a considerable distance from one another in the circumferential direction of the rotor can be found, for example, in FIG. 3 of DE-PS 25 26 657 and FIG. 3 of US Pat. No. 4,200,537; the last-mentioned state of the art shows strip-shaped profile elements with an approximately triangular cross-section, which have a first flank lying in front in the direction of rotation and projecting in the radial direction over the circumferential surface of the rotor body, that is to say approximately perpendicular to the circumferential surface of the rotor body, and a second flank sloping towards the rear. With the vertical front flank, the fiber suspension in the inlet area of the pressure sorter is accelerated in the direction of circulation and it also generates positive pressure surges, while negative pressure surges are generated with the falling second flank.

Further rotor shapes result e.g. from DD-PS 129 814 and US Pat. Nos. 3,912,622, 3,726,401 and 3,400,820; however, these known rotor shapes are irrelevant to the invention to be discussed below.

Other known proposals deal with the problem that such pressure impulses are generated in the fiber suspension by the cleaning blades or strip-shaped profile elements in the fiber suspension which are continuous in the direction of the sieve axis, such that they become disturbing in the headbox of a paper machine arranged downstream of the pressure sorter (this can result Form an uneven nonwoven fabric on the wire of a paper machine). The basic idea of the known solutions to this problem is to divide the profile elements transversely to the sieve axis into several segments and to fasten these segments on the circumferential surface of a circular cylindrical rotor body in such an arrangement that successive segments in the direction of the sieve or rotor axis are mutually offset in the circumferential direction of the rotor . The profile element segments of an axial rotor section each form a row in the rotor circumferential direction, with between There are two gaps in each case in two successive segments in the circumferential direction of the rotor and the lengths of the profile element segments and the gaps - measured in the circumferential direction of the rotor - are dimensioned in such a way and the offset mentioned was chosen such that - seen in the direction of the sieve or rotor axis - the profile element segments of an axial rotor section Cover gaps between the profile element segments of the adjacent axial rotor sections. An example of such a rotor design can be found in DE-PS 37 01 669 (see in particular Fig. 3); In this known rotor, the front faces or first flanks of the profile element segments lying in the direction of rotation were designed so that they have a concave, circular arc-shaped profile in section perpendicular to the rotor axis, which profile runs obliquely backwards and in the radial direction from the circumferential surface of the circular-cylindrical rotor body against the direction of rotation increases to the outside in order to reduce the impact effects of the pressure pulsations generated by the profile element segments (see column 1, lines 12-14 of DE-PS 37 01 669).

Finally, from US Pat. No. 4,855,038 and the latter corresponding EP-0 206 975-B, a pressure sorter of the type mentioned at the outset is known, the rotor of which is designed as a drum-shaped hollow body, the peripheral wall of the rotor body being two profile elements directly adjoining one another in the rotor circumferential direction forms, each of which has a vertical, first front flank lying in a diameter plane of the rotor and an adjoining second flank falling against the direction of rotation. Each of these profile elements extends in the direction of the rotor or sieve axis over the entire length of the rotor, so that this also applies to the front first flanks of the profile elements running parallel to the rotor axis. In addition, this known Pressure sorter on a circular cylindrical screen, the inlet side (even if the screen openings are disregarded) is not smooth, but rather profiled. The purpose of the design of the rotor and the inlet side of the sieve of this known pressure sorter is to continuously expose each area of the sieve to either a positive or a negative pressure pulse, due to the vertical front flanks of the profile elements and the resulting strong acceleration of the fiber suspension in the direction of rotation in Connection with the profiled inlet side of the sieve to generate strong turbulence in the fiber suspension located in the inlet area of the pressure sorter and finally, with the long, falling second flanks of the profile elements, to draw significant amounts of liquid from the accepted material space through the sieve back into the inlet area of the pressure sorter, in order to use a combination all of these measures to prevent the formation of a nonwoven on the inlet side of the screen with certainty.

A pressure sorter according to the preamble of claim 1 is known from US-A-4 744 894.

The invention had for its object to provide a pressure sorter of the type mentioned which, with relatively fine sieve openings, enables a good sorting result in all fiber suspensions to be processed which occur in practice and which in particular ensures trouble-free continuous operation.

Starting from a pressure sorter of the type mentioned at the outset with profile elements which extend in the circumferential direction of the rotor and in each case a first flank lying at the front in the direction of rotation for driving the fiber suspension in the direction of rotation and a second flank lying behind the first flank against the direction of rotation for sucking back liquid from the accept material space through the sieve into the inlet space, this can be Solve the task according to the invention in that in each axial section of the rotor peripheral surface acting on the screen, between two successive profile elements in the rotor peripheral direction, a rotor peripheral surface sector is provided, over which these profile elements protrude in the radial direction and which is part of a surface area parallel to the screen inlet side and rotationally symmetrical to the screen axis, whereby - Measured in the circumferential direction of the rotor - the maximum length of each profile element is at least approximately the same length as the minimum length of the rotor circumferential surface sector that follows in the opposite direction of rotation, but the minimum length of the latter is in each case at least approximately 30% of the maximum length of the profile element lying in front of it in the direction of rotation, and wherein the profile elements are designed and arranged on the rotor circumference in such a way that - viewed in the direction of the screen axis - the rotor circumferential surface sectors between the profiles elements along the area of the rotor encompassed by the sieve form continuous channels, and that the longitudinal direction of the first flank forms an acute angle with the axial direction.

Optimal sorting results can be achieved with a pressure sorter according to the invention, especially also with fiber suspensions of higher consistency to be processed, namely with a consistency of approx. 4% and more. This is due to the fact that on the one hand relatively long (measured in the rotor circumferential direction) profile elements are used, the front first flanks of which generate relatively high positive pressure surges and accelerate the fiber suspension in the direction of rotation strongly and the long, falling second flanks of larger quantities of liquid from the accept material space through the sieve suck into the inlet space, effects which counteract the formation of a nonwoven fabric on the inlet side of the sieve, but which, on the other hand, provide gaps in the circumferential direction between the profile elements, which - in the direction of rotation - be dimensioned so long that between the pressure pulsations generated by the profile elements a weak non-woven fabric can form on the inlet side of the screen, which acts as an auxiliary filter layer. The present invention thus teaches exactly the opposite of what is the basic idea of the pressure sorter according to US Pat. No. 4,855,038. On the other hand, in a pressure sorter according to the invention, a strong formation of non-woven fabrics cannot occur on the inlet side of the sieve, so that those disadvantages which a stronger fiber fleece has on the inlet side of the sieve can be avoided with such a pressure sorter. In particular, the following should be noted regarding the advantages and avoidable disadvantages that can be achieved with a pressure sorter according to the invention:

Fiber suspensions to be prepared from waste paper usually contain adhesive particles which are either plastically deformable from the start or plastically deformable at the normal operating temperatures of pressure sorters. The high positive pressure surges which are produced in a pressure sorter of the type described in US Pat. No. 4,855,038, however, in the absence of any nonwoven fabric on the inlet side of the sieve, result in a considerable part of such adhesive particles being pressed through even small sieve openings. A pressure sorter according to the invention avoids this disadvantage by producing a weakly formed nonwoven fabric due to the gaps between the profile elements.

A strong fiber fleece on the inlet side of the sieve leads to a strong fractionation of the fiber portion of a fiber suspension - long fibers, which are desirable per se in the accept, predominantly get into the reject, so that in the accept in an undesirable manner relatively short fibers predominate. Without any fiber fleece on the inlet side of the sieve, long-fiber impurities, such as hair, also get into the accept in an undesirable manner. Here, the pressure sorter according to the invention now leads to an optimization of the sorting effect, because a weakly formed non-woven fabric on the inlet side of the sieve allows long, brewable fibers to get into the accepted material to a considerable extent, while tests have shown that such a non-woven fabric has long-fiber impurities as it passes through through the sieve. In a pressure sorter according to the invention, the often undesirable strong fractionation of the fibers can be avoided.

In a pressure sorter according to the invention, the so-called rejects (the part of the fiber suspension to be reprocessed rejected by the sieve) is not thickened to such an extent that the sorting function of the device is permanently impaired in the region of the annular gap between the rotor and sieve adjacent to the second axial end of the inlet space. This is due on the one hand to the fact that the profile elements have relatively long falling second flanks and therefore suck back considerable amounts of liquid from the accept material space through the sieve into the inlet space, thereby diluting the rejects, and on the other hand the axial between the profile elements, from one to the other At the end of the inlet space or the rotor, through-going channels lead to a widening of the gap between the screen and the rotor circumference, so that relatively thin fiber suspension from the inlet-side end of the inlet space can flow relatively freely along these widened gap regions into those zones of the inlet space in which the to be processed fiber suspension due to drainage is already thicker through the sieve. In this context, it should be pointed out that in a pressure sorter, due to the pressure with which the fiber suspension to be processed is fed into the device, the fiber suspension in the inlet space has a flow component oriented parallel to the sieve or rotor axis. However, the widened gap regions caused by the gaps mentioned also result in this axial flow component being reduced (in comparison with conventional sorters, as shown in US Pat. No. 4,855,038 and DE-PS 37 Ol 669) (it stands overall, but above all in front of the front first flanks of the profile elements, an enlarged flow cross-section is available in the annular gap between the rotor circumference and sieve), which results in a reduction in the energy to be used for the rotor drive, because the steep front first flanks of the profile elements do not have such a strong longitudinal flow " cut through ".

Despite the formation of a light nonwoven fabric on the inlet side of the screen of the pressure sorter according to the invention, higher throughputs can be achieved with this screen than with a pressure sorter according to US Pat. No. 4,855,038 (provided that the screen openings are the same size) because they are known compared to the profile elements Pressure sorter shorter falling second flanks of the profile elements of the pressure sorter according to the invention result in shorter vacuum or suction phases during which the desired flow through the sieve from the inlet space into the accept material space cannot take place. This also shows that with the profile elements of the known pressure sorter according to US Pat. No. 4,855,038 - assuming the same throughput - higher positive pressure pulses must be generated, which is precisely what The absence of a non-woven fabric serving as an auxiliary filter layer results in a high percentage of the adhesive particles mentioned above being pressed through the sieve openings into the accept material space. The same applies due to the high positive pressure surges and the resulting high flow velocities through the sieve openings for long-fiber impurities contained in the fiber suspension to be processed.

As already mentioned, the front end faces or first flanks of the profile elements of the rotor of the known pressure sorter according to US Pat. No. 4,855,038 run exactly parallel to the sieve or rotor axis. In an advantageous embodiment of the pressure sorter according to the invention, however, the longitudinal direction of the first flank of each profile element forms an acute angle with the axial direction. This significantly extends the service life of the sieve; namely, it has been shown that in the known pressure sorter described, the sieve is at considerable risk of breakage, for several reasons, which will be discussed in more detail later, but above all for the following reason: As mentioned, profile elements forming a step form at the front strong positive pressure surges and thus pressure forces acting on the screen, which in the known pressure sorter are introduced into the screen along a surface line (a line parallel to the screen axis) due to the axial course of the front edges of the profile elements. Since, due to the flow resistance of the screen openings and the associated pressure drop across the screen to avoid even higher pump capacities for feeding a pressure sorter, efforts are made to make the screen of a pressure sorter as thin-walled as possible, the screen of the pressure sorter according to US Pat. No. 4,855,038 is in highly vulnerable to breakage. If now, as with the preferred embodiment of the pressure sorter according to the invention, which are slightly inclined in the direction of rotation of the first flanks of the profile elements with respect to the direction of the sieve axis, the introduction of the compressive forces, which cause the positive pressure surges generated by these first flanks, does not take place along a surface line of the sieve, and tests have confirmed that long-term breaks on the screen can be avoided.

To achieve the described advantage, the first flanks of the profile elements could be inclined in any direction with respect to the sieve axis. It would be conceivable, for example, that the inclination is chosen such that the first flanks of the profile elements exert an axial conveying effect on the fiber suspension located in the inflow space in the direction from the second axial end of the inflow space to its first axial end, as is the case with pressure sorters per se is known - in the rear part of the inlet space, already thickened fiber suspension to be reprocessed back in the axial direction and thereby to ensure a more uniform consistency of the fiber suspension to be sorted and an even more extensive separation of usable fibers into the accept material space. However, embodiments of the pressure sorter according to the invention are preferred in which the longitudinal direction of the first flank of each profile element is inclined relative to the axial direction in such a way that the first flanks exert an axial conveying effect on the fiber suspension located in the inflow chamber towards the second axial end of the inflow chamber. It has been shown that the sorting result can be improved even further as a result of this type of conveying effect, fiber suspension which has not yet thickened is intensified from the inlet-side end of the inlet space in the rear end thereof Area (the area facing the second axial end of the inlet space) is promoted and thereby the consistency of the fiber suspension to be sorted along (in the axial direction) of the rotor or the sieve is evened out.

Especially for embodiments of the pressure sorter according to the invention, in which the first flanks of the profile elements are inclined with respect to the axial direction, it is advisable to design and arrange the profile elements in such a way that the rear edge of the second flank runs parallel to the sieve axis, in order to narrow the to avoid clear cross-section of the aforementioned channels or the widened annular gap areas.

The first flanks of the profile elements at the front are intended to generate positive pressure surges and to drive the fiber suspension in the direction of rotation. Both can best be achieved by designing the profile elements in such a way that their first flank projects approximately in the radial direction over the rotor peripheral surface sector located in front of it. However, the first flank could also be slightly inclined with respect to the radial direction, namely obliquely inwards (in the direction of the rotor axis) and rear (counter to the direction of rotation), while first flanks inclined obliquely outwards and backwards (as in the DE- PS 37 01 669 shown) have the consequence that the fiber suspension located in front of a profile element is only pushed radially outwards against the screen and is not accelerated or is hardly accelerated in the direction of rotation.

In a pressure sorter according to the invention, each profile element can extend in the direction of the rotor axis over the entire length of the rotor circumference encompassed by the sieve; in this case the rotor has only one (in Rotor circumferential direction) row of profile elements and gaps arranged between them. Especially for the sorting of fiber suspensions with higher consistency, however, pressure sorters according to the invention with a different rotor design are recommended: Such pressure sorters are characterized in that the rotor has at least one first axial rotor circumferential surface section facing the first axial end of the inlet space and one adjacent to the latter in the axial direction second axial circumferential surface section, the first flanks of the profile elements of the second section being set back in relation to the first flanks of the profiled elements of the first section against the direction of rotation, and the lengths of the profiled elements measured in the circumferential direction of the rotor are dimensioned such that adjacent circumferential rotor sectors (gaps) in the axial direction of the two axial rotor sections overlap in the direction of rotation. The rotor of such a pressure sorter according to the invention thus has in particular two axial sections and thus two rows of profile elements (running in the rotor circumferential direction) and gaps arranged therebetween, the profile elements of one row and thus the gaps of this row compared to those of the other row only in the rotor circumferential direction are widely offset from one another that the gaps of both rows still form channels which extend in the axial direction over both rows or both rotor sections. The following additional advantages are achieved by such a rotor design: in the case of profile elements whose front first flanks extend from one to the other axial end of the rotor or sieve, there is above all if - as in the prior art - these first flanks are parallel run to the rotor axis, the risk that impurities and fibers contained in the fiber suspension to be sorted accumulate and clump these steep first flanks, which in particular harbors the risk that such material accumulations wedge between the radially outer edge of the first flanks and the sieve and thus render the pressure sorter inoperative or even lead to a sieve breakage. A staggered arrangement of the profile elements as described above now has the following effects, especially if the front first flanks are inclined relative to the axial direction in such a way that they have a conveying effect in the direction of the second axial end of the inlet space: that alone Axial flow through the annular gap between the rotor circumference and sieve (of the inlet space) caused by the delivery pressure in the inlet of the pressure sorter has the result that material accumulations on the first flanks of the profile elements of the first axial rotor section slide along these first flanks in the direction of the second axial end of the inlet space ; if these accumulations of material come to the edges of the profile elements of the first rotor section facing the second axial end of the inlet space, they are mixed there with fiber suspension due to the turbulence occurring there, so that the accumulations of material dissolve at least essentially before the fiber suspension of the next first flank Profile element of the second axial rotor section is detected. This axial derivation of undesirable accumulations of matter is of course intensified when the first flanks of the profile elements are inclined in the manner described. Due to the staggered arrangement of the profile elements described above, the fiber suspension to be sorted is also sufficiently fluidized in those areas of the annular space between the rotor circumference and sieve in which the consistency of the fiber suspension to be sorted has already risen as a result of the previous dewatering through the sieve, so that too a good sorting effect in these areas can be achieved. Furthermore, the staggered arrangement of the profile elements described above brings about an even better distribution of the pressure forces over the screen, ie those pressure forces which are generated by the positive pressure pulses caused by the profile elements and act on the screen.

In order to maintain the effect of the above-described channels or the widened areas of the annular gap between the rotor circumference and the screen to a sufficient extent in such a staggered arrangement of the profile elements, but also by a sufficient offset (in the direction of rotation) of the front first flanks adjacent to one another in the axial direction To provide profile elements for sufficient fluidization of the fiber suspension over the entire axial length of the sieve or rotor, in a particularly advantageous embodiment of the pressure sorter according to the invention with staggered profile elements, the overlap of one another in the axial direction of adjacent rotor peripheral surface sectors (gaps) - measured in the rotor peripheral direction - is at least approximately 50% of the length of one of the rotor peripheral surface sectors.

In principle, the profile elements of different axial rotor sections could be designed identically. However, it is advisable to take into account the different consistency of the fiber suspension to be sorted in the different axial areas of the annular space between the rotor circumference and sieve by a correspondingly different design of the profile elements, in order not to cause unnecessarily strong positive and negative pressure impulses either in certain axial areas of this annular space generate or too small in other axial areas of this annulus generate positive and negative pressure impulses. Therefore, for a preferred embodiment of a pressure sorter according to the invention with profile elements arranged in a staggered manner as described above, it is recommended to dimension the profile elements in the first axial rotor peripheral surface section - measured in the rotor peripheral direction - shorter than in the second rotor peripheral surface section. As an alternative or in addition to this measure, the height of the first flanks of the profile elements in the first axial rotor circumferential surface section measured in the radial direction can be dimensioned smaller than in the second rotor circumferential surface section for the same purpose.

As already mentioned, it is advisable to design the first flank of the profile elements in such a way that it can be used to effectively accelerate the fiber suspension in the direction of rotation. First flanks of the profile elements designed in this way are particularly advantageous since they can be used to accelerate the fiber suspension in the direction of rotation up to the circumferential speed of the rotor, because then maximum positive pressure pulses and particularly strong turbulence are generated by the profile elements.

The effect, the throughput and the sorting behavior of a pressure sorter depend to a considerable extent on the smallest radial distance of the profile elements from the screen, the design and arrangement of the profile elements, but very much also on the speed of rotation of the profile elements. In the case of a pressure sorter according to the invention, an increase in the speed of the rotor not only leads to stronger turbulence, but also to a weaker formation of the nonwoven fabric to a certain extent desired on the inlet side of the screen. The less such a nonwoven forms, in order the less undesirable fractionation of the fiber suspension or the fibers contained in it occurs, moreover, a less-formed nonwoven fabric leads to a higher consistency in the accept, to a lower consistency of the reject and finally to a reduction in the sorting purity. Naturally, an increase in the rotor speed ultimately leads to an increase in wear on the rotor and screen (fiber suspensions obtained from waste paper always contain abrasive contaminants such as sand and metal parts). On the other hand, the sorting of fiber suspensions of higher consistency or consistency requires a higher rotor speed than when sorting thinner fiber suspensions. Certain disadvantages of a higher rotor speed can now be avoided in a pressure sorter according to the invention by using shorter (measured in the circumferential direction of the rotor) and / or lower (measured in the radial direction) profile elements. For the sake of completeness, it should also be pointed out that higher rotational speeds of the profile elements allow sieves with finer sieve openings (bores of smaller diameter or narrower slots) to be used, which improves the sorting purity.

Pressure sorters which have become known to date have a rotor drive which only allows operation at a very specific rotor speed. However, it can be seen from the above explanations that it would be desirable per se to be able to operate the same pressure sorter at different rotor speeds, for example to take into account the consistency or consistency of the fiber suspension to be sorted or to be able to achieve certain sorting results. The invention now remedies this by proposing to use a three-phase motor as the motor for driving the rotor. which is preceded by a frequency converter that is controllable with regard to its output frequency. With a pressure sorter of this type, the rotor speed can thus be varied solely by changing the setting of the frequency converter and thus the frequency of the feed current for the three-phase motor, and can thus be adapted to the desired sorting method or sorting result.

Since in a certain pressure sorter according to the invention the strength of the nonwoven formation on the inlet side of the sieve depends crucially on the rotor speed and the strength of the nonwoven formation in turn influences the size of the pressure difference which occurs between the inlet side of the sieve and the other side of the sieve, i.e. there is between the inlet space and the accept material space, this pressure difference can be used according to the invention as a controlled variable for the frequency converter; In a preferred embodiment of the pressure sorter according to the invention, the frequency converter can thus be controlled by a measuring device for measuring the pressure difference between the inlet space and the accepting space. In this way, by specifying a desired pressure difference, the strength of the nonwoven formation on the inlet side of the screen and thus the sorting result can be specified.

Especially with regard to the rational production of a pressure sorter according to the invention and the fact that wear of the profile elements, especially in the region of their front first flanks, cannot be avoided, the invention proposes some particularly advantageous embodiments of the rotor of the pressure sorter according to the invention.

In an embodiment that can be produced without particularly complicated tools, the rotor has a circular-cylindrical and hollow rotor body, the peripheral surface of which Forms rotor circumferential surface sectors and in which the first flanks of the profile elements are formed by strips attached to the circumferential surface of the rotor body and the second flanks of the profile elements are formed by sheets which are curved in a side view, the front edges of which are fastened to the strips and the rear edges of which are fastened to the rotor body circumferential surface . The strips and sheets could be fastened, for example, by screws to the rotor body or to the strips, but embodiments are preferred in which the strips are welded onto the rotor body and / or in which the sheets are welded onto the strips and the rotor body. In the case of hollow profile elements that result, care is expediently taken to ensure that the cavities are closed in a liquid-tight manner in order to avoid the occurrence of imbalances. However, this problem can also be remedied by filling the cavities formed by the circumferential surface of the rotor body and the profile elements with a plastic, which can be, for example, a hardenable casting resin, but it is more advantageous if an in-situ foamed plastic is used , because it allows these cavities to be filled easily and completely so that liquid cannot penetrate into these cavities.

With profile elements designed in this way, the strips can be exchanged relatively easily, which is particularly important because the strips forming the front, first flanks of the profile elements are exposed to the greatest wear.

As an alternative, it is recommended according to the invention to design the profile elements as solid plastic bodies, which can be produced cheaply as plastic injection molded parts.

Such full plastic body profile elements could be replaced as a whole in the event of wear, but this is not necessary if the front face of the profile elements lying in the direction of rotation is formed by a metal strip, which e.g. is inserted into the all-plastic body, because then in the event of wear, only this metal strip normally has to be replaced.

If it is not possible to generate sufficient turbulence for certain sorting tasks with the aid of a rotor designed according to the invention and a sieve that is smooth on the inlet side, in order to prevent the formation of an excessively thick nonwoven fabric on the inlet side of the sieve, an embodiment of the pressure sorter according to the invention should be used which has a turbulence-generating profile on the inlet side of the sieve. Such profiles can be found in the prior art

Fig. 1

eine teilweise geschnittene Seitenansicht des erfindungsgemäßen Drucksortierers, wobei die Schnittdarstellung ein Schnitt in einer vertikalen Durchmesserebene des Rotors bzw. Siebs ist;

Fig. 2

einen Schnitt nach der Linie 2-2 in Fig. 1;

Fig. 3

Sieb und Rotor des Drucksortierers wie in Fig. 1 dargestellt, jedoch in größerem Maßstab als in Fig. 1;

Fig. 4

eine Stirnansicht des Rotors, gemäß Fig. 1 von links gesehen, und zwar samt in einem axialen Schnitt dargestelltem Sieb, und

Fig. 5

eine Abwicklung des Rotorumfangs, d.h. eine Draufsicht auf die gesamte Rotorumfangsfläche, welche jedoch in einer Ebene dargestellt wurde.

Further features, advantages and details of the invention result from the appended claims and / or from the following description of a particularly advantageous embodiment of the pressure sorter according to the invention with reference to the accompanying drawing; show in the drawing:

Fig. 1

a partially sectioned side view of the pressure sorter according to the invention, the sectional view being a section in a vertical diameter plane of the rotor or sieve;

Fig. 2

a section along the line 2-2 in Fig. 1;

Fig. 3

Sieve and rotor of the pressure sorter as shown in Fig. 1, but on a larger scale than in Fig. 1;

Fig. 4

a front view of the rotor, as seen in FIG. 1 from the left, including the sieve shown in an axial section, and

Fig. 5

a development of the rotor circumference, ie a plan view of the entire rotor circumferential surface, which was, however, shown in one plane.

The actual pressure sorter 10 shown in FIG. 1 with a housing 14 standing on supports 12 also includes a motor 18 standing on a frame 16, which is a three-phase or three-phase AC motor, which is operated by means of a pulley 20 and V-belt 22 drives a pulley 24, which is fastened on a rotor shaft 26 rotatably mounted in the frame 16 and the housing 14.

The housing 14 essentially consists of a left end wall 28 according to FIG. 1, a circular cylindrical housing jacket 30 arranged concentrically to the rotor shaft 26 and a housing cover 32 which are connected to one another in a pressure-tight manner. An axis of the pressure sorter, which is also the axis of the rotor shaft 26, was designated 34.

The rotor shaft 26, which is passed through the end wall 28 in a pressure-tight manner, carries a rotor, designated as a whole by 36, which can be driven about the axis 34 by means of the rotor shaft 26 and is surrounded by a circular cylindrical sieve 38 which is concentric with the axis 34 and which is attached to two on the housing jacket 30 attached annular housing elements 40 and 42 is fixed and is held by these housing rings.

In the illustrated embodiment, the axial length (in the direction of the axis 34) of the rotor 36 is equal to the axial length of the effective area of the screen 38 between the housing rings 40 and 42. However, it would also be possible to achieve the effects of the axial length of the rotor 36 to be chosen larger or smaller than the axial length of the sieve 38.

At the right end of the housing 14 according to FIG. 1, an inlet connection 46 is provided, through which - as indicated by the arrow F - the fiber suspension to be processed or sorted is conveyed into the pressure sorter, by means of a pump, not shown. Approximately in the middle above the screen 38, an outlet connection 48 is attached to the housing jacket 30, through which the so-called accept material - as indicated by the arrow A - leaves the pressure sorter. The accepted substance is the part of the fiber suspension that has passed the sieve 38. At the left end of the housing casing 30 according to FIG. 1, a second outlet connection 50 is finally fastened, through which the so-called rejects - as indicated by the arrow R in FIG. 2 - leaves the pressure sorter; the reject material is the part of the fiber suspension to be processed which cannot pass through the sieve 38.

Advantageously, the inlet connection 46 will be arranged contrary to the illustration in FIG. 1 so that the fiber suspension to be sorted flows approximately tangentially into the housing 14, just as the outlet connection 50 for the rejects is oriented tangentially (see FIG. 2). In addition, the outlet connection 48 could of course also be arranged at the bottom of the housing jacket 30, insofar as the installation of the pressure sorter 10 permits the removal of the accepted substance downwards.

Insofar as the construction of the pressure sorter has been described above, this is known from the prior art, and this also applies to its basic function insofar as it is described below (deviations according to the invention will only be discussed after the description of the basic function).

The fiber suspension to be processed, which is fed into the pressure sorter 10 via an inlet connection 46, first arrives in an inlet space 52 and then enters an annular space between the circumference of the rotor 36 and the sieve 38, which will be referred to below as the inlet space 54, namely the fiber suspension to be sorted into the latter via a first axial end 54a of this inlet space. As a result of the rotor 36 rotating about the axis 34 and, if appropriate, the tangential orientation of the inlet connector 46 and due to the pressure under which the fiber suspension to be sorted is conveyed into the pressure sorter 10, the fiber suspension flows helically through the inlet space 54 from its first end 54a the second end 54b thereof, part of the fiber suspension passing through openings in the sieve 38 and thus entering the accepting material space 58. The reject leaves the inlet space 54 at its second end 54b and thus arrives in the reject space 56, from which the reject leaves the pressure sorter via the second outlet connection 50.

In preferred embodiments of the pressure sorter according to the invention, the axis 34 runs at least approximately horizontally, but in principle it would also be conceivable to set up the pressure sorter in such a way that its axis 34 runs at least approximately vertically.

The features of the pressure sorter according to the invention and of the sorting method carried out by this are explained below.

Because of the relatively fine openings of the sieve 38, there is a pressure difference between the inlet space 54 and the accept material space 58, namely the pressure in the accept material space is lower than in the inlet space. In order to detect this pressure difference, a measuring device 60 is provided according to the invention, which comprises a first pressure transmitter 62 and a second pressure transmitter 64, which are arranged in the inlet connector 46 and in the first outlet connector 48, but also also in the inlet chamber 52 or in the accept material chamber 58 could be. They are connected via lines 66 and 68, in which display devices 70 and 72 are arranged, to the inputs of a difference former 74, which delivers at its output a control signal proportional to the pressure difference, which is applied via line 76 to the control input of a frequency converter 78. This is fed from a current source, not shown, with a 3-phase alternating current or three-phase current of frequency f ₁ and supplies a three-phase current of frequency f ₂ for driving three-phase motor 18, frequency f _{2 being} a function of the control signal generated by difference generator 74. In this way, the rotor 36 is driven at a speed which is a function of this control signal and thus the pressure difference between the inlet space 54 and the accept material space 58. Instead of or in addition to the display devices 70 and 72, potentiometers or other actuating elements could also be provided in the lines 66 and 68, by means of which the signals supplied by the pressure transmitters 62 and 64 can be changed, in order in this way to make the dependence on the line 76 possible To be able to influence the control signal from the pressure difference mentioned.

The design of the rotor 36 according to the invention will now be explained in more detail with reference to FIGS. 3 to 5.

A hub 80 fixedly connected to the rotor shaft 26 carries a closed, hollow circular cylindrical rotor body 82 with a circular cylindrical rotor jacket 84. This has a first axial end 84a at the first axial end 54a of the inlet space 54 and a second axial end 84b at the second axial end 54b of the Inlet space and outside carries two sets of profile elements, namely a first set, which is formed by profile elements 86a, 86b, 86c and 86d, and a second set, formed by profile elements 88a, 88b, 88c and 88d. The first set of profile elements forms a first row of profile elements extending in the rotor circumferential direction or direction of rotation U of the rotor and gaps 86a ', 86b', 86c 'and 86d' arranged between them, and this row defines a first axial rotor section 90 which defines the inlet space 52 faces; the second set of profile elements 88a-88d forms a second, likewise row of profile elements and gaps 88a ', 88b', 88c 'and 88d' arranged between them, and this second row defines a second axial rotor section 92, which is adjacent to the rejects space 56. In the preferred embodiment shown, all profile elements are of the same height (measured in the direction of the axis 34), but depending on the desired sorting result and / or depending on the type of fiber suspension to be sorted, it could be expedient to increase or decrease the height of the first row choose as the height of the second row. It may also be expedient to provide the rotor with more than two such rows.

As can be seen in particular from FIGS. 2 and 4, each profile element has a front lying in the direction of rotation U. End face or first flank I, which runs perpendicular to the circular-cylindrical outer circumferential surface of the rotor shell 84 and thus to the surface of the gap lying in front of it in the direction of rotation U, and a back surface or second flank II directly adjoining the first flank I, which runs counter to the direction of rotation U in a radial direction Direction inwards and thus falls towards the axis 34, so that the profile elements have a cross section perpendicular to the axis 34 which is similar to a very acute-angled triangle which was bent concentrically to the axis 34. With the first flanks, strong positive pressure surges and strong turbulence are generated in the inlet space 54, and with the first flanks I the fiber suspension in the inlet space 54 is strongly accelerated, at most up to the rotational speed of the profile elements. In contrast, the falling second flanks II generate negative pressure pulses, by means of which liquid is sucked back from the accept material space 58 through the sieve openings into the inlet space 54. Particularly strong turbulence occurs in the inlet space 54 as a result of the flow component of the fiber suspension directed in the direction of rotation U when the inside of the sieve 38 is “rough” in a known manner, ie is profiled; since sieves profiled in this way are known to pressure sorters and suitable profiles are difficult to depict in the accompanying drawings, this profiling cannot be found in the drawings.

According to the invention, in preferred embodiments of the pressure sorter according to the invention, the first flanks I do not run parallel to the axis 34, but form an acute angle a with the direction of the axis 34, and in fact the flanks are inclined with respect to the direction of the axis 34, so that the direction the flow component of the fiber suspension in the axis 34 Inlet space 54 is reinforced in the direction from the first axial end 54a of the inlet space to the second axial end 54b thereof

As can be seen from FIG. 5, in the preferred embodiment shown, the profile elements 86a-86d of the first row - measured in the rotor circumferential direction or direction of rotation U - are shorter than the profile elements 88a-88d of the second row. This measure serves the purpose of adapting the effect of the profile elements to the different consistency of the fiber suspension, the consistency of which increases in the inlet space 54 from its first end 54a to its second end 54. In the particularly advantageous embodiment shown in FIG. 5, each of the profile elements 86a-86d of the first row extends over a circumferential angle of 45 ° (this is the maximum length L _{1 of} the profile elements), the length of the profile elements to the second axial end 84b of the Rotor jacket 84 decreases because the first flanks run obliquely to the direction of the axis 34, while the rear edges of the second flanks II are aligned parallel to the axis 34. The smallest length L ₁ 'of the gaps 86a' - 86d 'of the first row is also 45 ° and is therefore equal to the greatest length L _{1 of} the profile elements of this row, the length of the gaps in the direction of the second axial end 84b of the rotor shell 84 increases.

The maximum length L _{2 of} the profile elements 88a-88d of the second row is 53 ° in this embodiment; Since, according to the invention, the number of profile elements of the second row is equal to the number of profile elements of the first row, the minimum length L ₂ 'of the gaps 88a' - 88d 'of the second row results in a lower value of 37 ° here.

As can also be seen in FIG. 5, the profile elements 88a-88d of the second row and thus their gaps are offset relative to the profile elements of the first row or their gaps against the direction of rotation U, the size of the offset thus being based on the lengths of the profile elements or the gaps are coordinated so that adjacent gaps of the two rows in the axial direction overlap in the direction of rotation U or in the rotor circumferential direction to such an extent that they form a continuous channel in the axial direction which extends from one axial end 84a of the rotor shell 84 to whose other axial end 84b extends. In the embodiment shown in FIG. 5, the inside width L _{3 of} this channel is 25 °, the inside width being understood as the width which the observer sees in the direction of the axis 34 when the rotor is viewed from the front.

In the preferred embodiment shown, the lengths of the profile elements of the first row are therefore approximately equal to the lengths of the gaps of the first row, the lengths of the profile elements of the second row are greater than the lengths of the profile elements of the first row, and the length of the gaps of the second row are smaller than the lengths of the profile elements in the second row and smaller than the lengths of the gaps in the first row.

The arrangement of the profile elements of the two rows according to the invention results in steps 90, by means of which the following effect is achieved: accumulations of fibers and impurities, which can occur on the first flanks of the profile elements 86a-86d of the first row, slide due to the axial flow component of the Fiber suspension in the inlet space 54 along the first flanks I of the profile elements of the first row in the direction of the second axial end 54b of the inlet space 54 and thus reach the steps 90, in the area of which they are dissolved due to the strong turbulence there and mixed with the fiber suspension - accumulations of fibers and impurities on the first flanks I of the profile elements 88a-88d of the second Row are also transported in the axial direction and enter the reject space 56.

The lengths of the profile elements and the gaps were expressed in circumferential angles above. In practical implementation of the pressure sorter according to the invention, the lengths L ₁ and L _{2 are} in a range between approximately 200 mm and approximately 450 mm.

The circumferential speeds of the rotor achieved by adjusting the rotor speed are expediently between approximately 10 m / s and approximately 40 m / s, the best sorting results generally being achieved with circumferential speeds of approximately 15 to approximately 30 m / s.

If the sieve openings 38a of the sieve 38 are bores, their diameter is expediently approximately 1 mm to approximately 3.5 mm if the rotor is operated at a peripheral speed of approximately 10 to approximately 15 m / s . Smaller holes can be used at higher peripheral speeds; expediently one operates a pressure sorter according to the invention with rotor peripheral speeds of approx. 15 to approx. 40 m / s and then chooses bores with a diameter of approx. 0.5 to approx. 1.5 mm for the sieve openings. If the screen openings 38a are slits, then these should have a rotor circumferential speed of approximately 10 to approximately 15 m / s Have a width of about 0.4 to about 0.6 mm; Even in the case of slots, finer screen openings can be used at higher rotor peripheral speeds, and since rotor peripheral speeds of approximately 15 to approximately 40 m / s are preferred, slot-shaped screen openings with a width of approximately 0.1 mm to approximately 0.35 mm recommended.

3 and 4 show the structure of the profile elements 86a-86d and 88a-88d of the preferred embodiment shown. Each of these profile elements consists - apart from the rotor casing 84 - of a strip 100 forming the first flank I, a bent sheet 102 forming the second flank II and two side walls 104, reference being made to FIG. 3 to indicate that in this figure because of the oblique course of the first flanks and thus the strips 100 the latter were not cut perpendicular to their longitudinal extension, but obliquely thereto. The cavities 106 of the profile elements enclosed by the rotor jacket 84, the strips 100, the sheets 102 and the side walls 104 should be liquid-tight or filled with a filler such as e.g. a foam plastic, to avoid imbalances in the rotor. The same applies to the cavity of the rotor body 82.

Finally, it should be pointed out that the channels with the clear width L _{3 can be seen} particularly clearly from FIG. 4 and have been designated 200 there.

Claims (28)

1. Pressure sorter (10) for fibre suspensions, in particular, for the preparation of fibre suspensions obtained from waste paper, comprising a housing (14) in which a stationary screen (38) is arranged, said screen being rotationally symmetrical to a screen axis (34) and separating in said housing a supply chamber (54) surrounded by said screen from an accepts chamber (58) lying outside said screen, as well as a rotor (36) drivable about the screen axis by a motor (18), the circumferential surface of said rotor together with an inlet side of the screen delimiting the supply chamber in the radial direction, an inlet (46) for the fibre suspension to be treated communicating with a first axial end (54a) of the supply chamber (54), and a rejects outlet (50) communicating with a second axial end (54b) of the supply chamber (54), profiled elements (86a - 86d, 88a - 88d) being provided at the circumferential surface of the rotor (36) for generating positive and negative pressure pulses in the fibre suspension, said profiled elements extending in the circumferential direction of the rotor as well as in the direction of the screen axis (34) and each having a first flank (I) lying in front in the rotational direction (U) for driving the fibre suspension in the rotational direction as well as a second flank (II) lying behind the first flank in a direction opposite to the direction of rotation for sucking back liquid from the accepts chamber (58) through the screen (38) into the supply chamber (54), characterized in that in every axial section (90, 92) of the circumferential surface of the rotor acting on the screen (38), a rotor peripheral surface sector (86a' - 86d', 88a' - 88d') is provided between two profiled elements (86a - 86d, 88a - 88d) following one another in the circumferential direction of the rotor, these profiled elements protruding in the radial direction beyond said rotor peripheral surface sector and said rotor peripheral surface sector being part of a peripheral surface area (84) parallel to the screen inlet side as well as rotationally symmetrical to the screen axis (34), in that - measured in the circumferential direction of the rotor - the maximum length (L1, L2) of each profiled element (86a - 86d, 88a - 88d) is at least equal to the approximate minimum length (L1', L2') of the rotor peripheral surface sector (86a' - 86d', 88a' - 88d') following in a direction opposite to the direction of rotation (U), but the minimum length (L1', L2') of said rotor peripheral surface sector is at least 30 % of the approximate maximum length (L1, L2) of the profiled element lying in front thereof in the direction of rotation, and the profiled elements (86a - 86d, 88a - 88d) are designed and arranged at the rotor circumference such that - seen in the direction of the screen axis (34) - the rotor peripheral surface sectors (86a' - 86d', 88a' - 88d') form continuous channels (200) between the profiled elements along the region of the rotor (36) surrounded by the screen (38), and in that the longitudinal direction of the first flank (I) forms an acute angle (α) with the axial direction (34).
2. Pressure sorter according to claim 1, characterized in that the longitudinal direction of the first flank is inclined with respect to the axial direction such that the first flank exerts on the fibre suspension present in the supply chamber an axial conveying effect towards the second axial end of the supply chamber.
3. Pressure sorter according to claim 1 or 2, characterized in that the rear edge of the second flank extends parallel to the screen axis.
4. Pressure sorter according to one or several of claims 1 to 3, characterized in that the first flank protrudes approximately in the radial direction beyond the rotor peripheral surface sector lying in front of said flank.
5. Pressure sorter according to one or several of claims 1 to 4, characterized in that the rotor has at least one first axial rotor circumferential surface section facing the first axial end of the supply chamber as well as a second axial rotor circumferential surface section adjacent to said first axial rotor circumferential surface section in the axial direction, the first flanks of the profiled elements of the second section being set back with respect to the first flanks of the profiled elements of the first section in a direction opposite to the direction of rotation, and the lengths of the profiled elements measured in the circumferential direction of the rotor being dimensioned such that rotor peripheral surface sectors of the two axial sections adjacent to each other in the axial direction overlap each other in the direction of rotation.
6. Pressure sorter according to claim 5, characterized in that the overlapping - measured in the circumferential direction of the rotor - is at least approximately 50 % of the length of one of the rotor peripheral surface sectors.
7. Pressure sorter according to claim 5 or 6, characterized in that the profiled elements in the first axial rotor circumferential surface section - measured in the circumferential direction of the rotor - are shorter than in the second section.
8. Pressure sorter according to one or several of claims 5 to 7, characterized in that the height of the first flanks of the profiled elements - measured in the radial direction - in the first axial rotor circumferential surface section is smaller than in the second section.
9. Pressure sorter according to one or several of the preceding claims, characterized in that the motor is a three-phase A.C. motor supplied by a frequency converter controllable with respect to its output frequency.
10. Pressure sorter according to claim 9, characterized in that the frequency converter is controllable by a measuring device for measuring the pressure difference between supply chamber and accepts chamber.
11. Pressure sorter according to one or several of the preceding claims, characterized in that the rotor has a circular-cylindrical and hollow rotor body, the peripheral surface of said rotor body forming the rotor peripheral surface sectors, in that the first flanks of the profiled elements are formed by strips attached to the peripheral surface of the rotor body and the second flanks by metal sheets which, in the side view, are arcuately curved, the front edges of said sheets being attached to the strips and their back edges to the peripheral surface of the rotor body.
12. Pressure sorter according to claim 11, characterized in that the strips are welded onto the rotor body.
13. Pressure sorter according to claim 11 or 12, characterized in that the metal sheets are welded onto the strips and the rotor body.
14. Pressure sorter according to one or several of claims 11 to 13, characterized in that cavities formed by the peripheral wall of the rotor body and the profiled elements are sealed.
15. Pressure sorter according to one or several of claims 11 to 14, characterized in that cavities formed by the peripheral wall of the rotor body and the profiled elements are filled with a plastic material.
16. Pressure sorter according to claim 15, characterized in that the plastic material is a foam plastic foamed in-situ.
17. Pressure sorter according to one or several of claims 1 to 10, characterized in that the profiled elements are solid plastic bodies.
18. Pressure sorter according to claim 17, characterized in that the front surface of the profiled elements lying in front in the direction of rotation is formed by a metal strip.
19. Pressure sorter according to one or several of the preceding claims, characterized in that the inlet side of the screen has a turbulence-generating profile.
20. Pressure sorter according to one or several of the preceding claims, characterized in that the length of the profiled elements measured in the circumferential direction of the rotor is approximately 200 mm to 450 mm.
21. Pressure sorter according to one or several of the preceding claims, characterized in that the rotor is drivable by the motor at a circumferential speed of approximately 10 to 40 m/s.
22. Pressure sorter according to claim 21, characterized in that the rotor is drivable by the motor at a circumferential speed of approximately 15 to 30 m/s.
23. Pressure sorter according to one or several of the preceding claims, characterized in that for a rotor with a circumferential speed of approximately 10 to 15 m/s the screen has screen openings in the form of bores with a diameter of approximately 1 to 3.5 mm.
24. Pressure sorter according to one or several of claims 1 to 22, characterized in that for a rotor with a circumferential speed of approximately 15 to 40 m/s the screen has screen openings in the form of bores with a diameter of approximately 0.5 to 1.5 mm.
25. Pressure sorter according to one or several of claims 1 to 22, characterized in that for a rotor with a circumferential speed of approximately 10 to 15 m/s the screen has screen openings in the form of slots with a width of approximately 0.4 to 0.6 mm.
26. Pressure sorter according to one or several of claims 1 to 22, characterized in that for a rotor with a circumferential speed of approximately 15 to 40 m/s the screen has screen openings in the form of slots with a width of approximately 0.1 to 0.35 mm.
27. Pressure sorter according to one or several of the preceding claims, characterized in that the first flank of the profiled elements is designed such that the fibre suspension can be accelerated therewith in the direction of rotation up to the circumferential speed of the rotor.
28. Pressure sorter according to one or several of claims 5 to 8, characterized in that profiled elements adjacent to each other in the axial direction directly adjoin each other in the axial direction.

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