EP0905309B1 - Screen and pressure screening device for fibre suspensions - Google Patents

Abstract

A sieve, for sorting a fibre suspension in pressure sorting machines with a rotating rotor, is formed as a symmetrical cylinder about a shaft and it has, to sort the suspension, an inflow and an opposite outflow side. The rotor has, extending around its circumference and for generating positive and negative pressure pulses in the suspension, revolving profiled pieces approaching the inflow side. On the sieve inflow side round its circumference are grooves running parallel to the shaft, where at least one passage opens into each and where each has a floor, a front and a rear wall as viewed from the rotation direction of the profiled pieces. The passage opens into the floor and the front wall is more steeply tilted, i.e. at an angle between 40 and 70 deg., w.r.t. sieve circumference than the rear. In a section right angles to the shaft (34) the groove (400) has a V-shaped cross-section. Also claimed is a sorter with a casing and the fixed sieve separating an enclosed flow space from an outer product chamber. Together with inflow side, the rotor rotating outer surface bounds the flow space which, along the shaft, has an inlet for the suspension at one end and a waste outlet at the other. The profiled pieces each have a forward lying first side-piece for driving the suspension forwards and behind it a second piece lying in the opposite direction for sucking fluid back from the outer chamber.

Description

The invention relates to a sieve according to the preamble of the claim 1 and a pressure sorter according to the preamble of Claim 28.

In particular, the invention relates to such screens, at which the upstream grooves and the sieve passage channels in a screen wall that is rotationally symmetrical to the screen axis from one stainless steel sheet are formed, or such pressure sorters, as described in WO 94/00634 from Hermann Finckh Maschinenfabrik GmbH & Co. reveals and claims become.

A sieve with the features of the preamble of claim 1 can be seen from Figures 14 to 16 of EP-A-0 205 623. How 14 of this document, the upstream grooves continuously over the entire axial length the effective part of the sieve, and each of these grooves are assigned several sieve passage channels, which as in Slits extending in the direction of the sieve axis are formed are successive in the direction of the sieve axis and in this direction are spaced from each other. The Profile of the upstream grooves is designed so that the in Direction of rotation of the fiber suspension to be sorted at the front horizontal groove side wall - on average perpendicular to the sieve axis - forms an angle of 90 ° with the circumferential direction of the sieve and the two groove side walls form an angle with each other of approximately Form 135 °. The width measured in the direction of the wire circumference the non-profiled and parallel to the wire circumferential direction running surface areas of the sieve between the in Sieve circumferential direction of successive grooves is clear larger than that on the upstream side of the sieve as well Width of the grooves measured in the circumferential direction of the sieve.

A similar sieve results from Fig. 2a the US-A-4 529 520, however this known strainer has on it Upstream side between successive in the circumferential direction of the screen Grooves no parallel to the direction of the wire circumference Surface areas.

The influence of the profile of the upstream side of the sieve from Print sorters, but also the design and arrangement the actual sieve openings determining the sorting fineness or sieve passage channels on the operating behavior of Print sorter screen is detailed in the following articles the magazine "Das Papier", year 1994, issues 4, 5 and 10 described: "Influence of slot contours on the fiber passage - Examination with the help of a model sorter ", Pages 172 - 179 and 235 - 247, as well as "Modeling the Fiber passage behavior in suspension flow through sorting slots ", Pages 635 - 638. In Fig. 5 on page 177 of the essay mentioned in the first place are by grooves contoured upstream sides of pressure sorter screens shown, in whose Siebdurchlaßkanäle it is parallel to Sieve axis extending and radial with respect to the latter flows through slits and their grooves also run parallel to the sieve axis and on average perpendicular to the Sieve axes have a V-shaped cross section, the bisector of the angle runs radially with respect to the sieve axis, whereby the slot-shaped sieve passage channels either exactly in the bottom of the groove open or in the front seen in the direction of rotor rotation or rear groove side wall, each approximately halfway up the groove side wall in question. The two Groove side walls are opposite to the screen circumferential direction, respectively inclined at an angle of 45 ° so that they join together Form an angle of 90 °. The groove depth is 1 mm, the in The groove width measured as a result of this is 2 mm.

With regard to their operating behavior in pressure sorters of the At the beginning of the type, such screens are particularly popular Hermann Finckh Maschinenfabrik GmbH & Co. has proven which a screen wall that is rotationally symmetrical to the screen axis have a stainless steel sheet on the upstream side successive in the circumferential direction of the sieve and have grooves running approximately parallel to the sieve axis, each of which is on average perpendicular to the sieve axis Has a V-shaped cross-section with respect to its bisector the sieve axis runs radially, with the two groove side walls enclose an angle of 120 ° between them and which also flowed radially with respect to the sieve axis Sieve passage opens into the bottom of the groove. In terms of the radial axis measured are the Grooves between 0.8 mm and 1.0 mm deep (for sorting Fiber suspensions with a relatively short majority Fibers, a smaller groove depth has proven to be advantageous a larger groove depth for long fibers). On the upstream side of the sieve is between in its circumferential direction successive grooves are each essentially flat and at least approximately parallel to the wire circumferential direction Surface area provided, in the circumferential direction of the screen measured width is 0.5 mm. This profiling of the upstream side has proven itself for the following reasons:

So that the sieve passage channels in the operation of a pressure sorter not due to the fiber suspension to be sorted Impurities are clogged on the upstream side and become high throughput of fiber suspension to be treated per unit of time results in the fiber suspension to be sorted the upstream side of the sieve with the help of the rotor in it Circulation direction accelerated and driven, and by a appropriate profiling of the rotor circumferential surface thereby positive and in the fiber suspension to be sorted generated negative pressure surges. Due to the negative pressure surges becomes from that part of the fiber suspension that the sieve has already repeatedly passed through the fluid Suction passages sucked back through to the upstream side of the sieve, which flushes the sieve passages and clogs be prevented. Furthermore, in the on the To be sorted along the upstream side of the screen Fiber suspension generated turbulence due to the grooves; by which is prevented from being on the upstream side of the sieve reducing the throughput of the pressure sorter Can form nonwoven, which is also useful Fibers would be retained. For this purpose sufficiently strong turbulence requires a certain amount Minimum depth of said grooves. For training this Turbulences are those to be sorted in the direction of rotation Fiber suspension causes the first, front groove side walls; these generate mainly in the circumferential direction because of the rotor of the sieve flowing along its upstream side, Fiber suspension still to be sorted in the area of the respective front groove side wall a negative pressure, the greater is, the steeper this front groove side wall is, d. H. ever more this (on average perpendicular to the sieve axis) compared to the Sieve circumferential direction is inclined. A high such negative pressure but naturally leads to a reduction in throughput of the pressure sorter. That part of the Fiber suspension flowing along the sieve, which due to the said negative pressure into the groove is redirected, partially meets in the direction of flow rear, second groove side wall and is through this in the Main flow of the fiber suspension still to be sorted into it redirected, causing a nascent Nonwoven is at least partially destroyed again. Because of the flow pattern described in the groove is also understandable that a downstream, i.e. H. rear groove side wall opening into the sieve passage Danger is relatively quick due to fibers and in impurities contained in the fiber suspension, fiber bundles and the like to be plugged. With all of these Processes also allude to abrasive wear on the sieve its upstream side plays a significant role: especially from Fiber suspensions obtained from waste paper contain many different types abrasive components, such as sand, from wires, Metallic clips coming from paper clips and the like Components and the like. The more the abrasive wear the upstream side has progressed, the lower the depth of the grooves and the weaker they become for the Keep the sieve passages free of indispensable turbulence. For this reason, the grooves must also be fitted with a certain minimum depth. Mainly because of it is this abrasive wear on the upstream side of the screen also advantageous if on the upstream side between the Grooves flat and parallel to the screen circumferential surface areas be provided because if the grooves in Would directly adjoin the circumferential direction of the screen, would result in acute angles (on average perpendicular to the sieve axis) Contours between the rear groove side wall and the front groove side wall of two successive grooves, what contours from the abrasive components of the fiber suspension would be sanded down quickly, that the groove depth decreases rapidly and the turbulence rapidly would weaken.

Now, pressure sorters are getting higher throughputs required; the throughput depends essentially from the so-called free passage area of the sieve (Sum of the clear cross-sectional areas of the sieve passage channels), the given length and given with a sieve Diameter, the greater the more sieve passage channels and thus the more grooves the sieve has, d. H. ever the so-called division of the sieve is smaller (in the circumferential direction of the sieve measured distance of the centers from in this direction successive sieve passage channels). In the above described pressure sorter screen from Hermann Finckh Maschinenfabrik GmbH & Co., which is an extremely inexpensive Shows operating behavior, the sieve division is each depending on the groove depth 3.2 - 4.0 mm.

At Hermann Finckh Maschinenfabrik GmbH & Co. with their seven experiments described above have now shown that an increase in throughput by increasing the free passage area of the sieve by reducing the sieve division due to a reduction of the angle formed by the two groove side walls (also in the sense of reducing the sieve division an effective reduction of the groove depth is prohibited for the reasons described above because of the associated Weakening of the turbulence) is not possible but even a reduction in throughput because of quickly clogging sieve passages as well leads to the proportion of longer, still usable fibers, that pass through the sieve and reach its downstream side can be reduced in an undesirable manner.

The invention was based on the task of a sieve has upstream turbulence-generating grooves, or to create a pressure sorter with such a sieve which has a higher throughput than with the above known sieves or pressure sorters described with such Seven can be achieved without including his Wear behavior dependent durability or service life of the sieve.

This task can be done according to the invention with a sieve Solve claim 1 or a pressure sorter according to claim 25.

By the degree of inclination of the front according to the invention Groove side wall is achieved on the one hand, that on the upstream side the desired turbulence of the sieve, on the other hand but is by the front groove side wall on inflow end of the sieve opening caused negative pressure limited - the higher this vacuum, the lower is the throughput of the sieve. It has also been shown that the claimed inclination of the rear Groove side wall against the front groove side wall positive on the achievable throughput of the sieve affects. Finally leads the inventive dimensioning between the upstream Grooved surface areas of the sieve to optimize throughput performance taking into account the demand for a sufficient service life of the Sieve: The smaller the so-called division of the sieve (in the direction of the sieve circumference measured distance between two successive. Sieve openings from each other), the higher the achievable throughput; on the other hand lead to small ones (measured in the circumferential direction of the sieve) Siebs between the upstream grooves to a quick Wear on the upstream side of the screen and thus to one rapid reduction in throughput due to reduction the one required to keep the sieve openings clear Turbulence in the fiber suspension to be sorted.

Experiments have shown that with a sieve according to the invention with relatively low consistency of the ones to be sorted Fiber suspension is the amount of fiber suspension that can be processed per unit of time proportional to the increase in free Passage area of the sieve increases with increasing material density the fiber suspension even disproportionately, without a sieve according to the invention would be more susceptible to wear than that Known sieve from the Hermann company described above Finckh Maschinenfabrik GmbH & Co.

A pressure sorter screen with upstream, facing of the sieve axis extending grooves and sieve passage channels in The form of bores results from EP-B-0 456 788 Hermann Finckh Maschinenfabrik GmbH & Co. But also at this known strainer has each of the upstream grooves Section perpendicular to the sieve axis, a V-shaped cross-section, whose bisector is radial with respect to the sieve axis, with the two groove side walls one between them Include an angle of approx. 120 ° so that this sieve can also be used the above statements on the other known sieve of Hermann Finckh Maschinenfabrik GmbH & Co. apply. The sieve resulting from EP-B-0 456 788 opens into each of the upstream grooves a plurality of sieve passage channels (Holes) in the direction of the sieve axis at a distance from each other are arranged and each in one on the outflow side of the sieve provided opening, which the shape a frustoconical (in plan view of the downstream side of the sieve circular) countersink.

EP-A-0 521 192 discloses a cylindrical sieve for sorting of fiber suspensions become known, the screen wall has recesses on the upstream side of the sieve, in the each has a plate-shaped sieve insert, which a series of perpendicular to the platelet plane Has holes; these holes form the fineness of sorting determining sieve passage channels, and to each upstream One recess belongs from the downstream side of the Siebs forth in the sieve wall made hole, the axis runs perpendicular to the screen wall and its diameter is so large is dimensioned that all holes of the sieve insert in this Hole. The recesses in which the sieve inserts are used when looking at the screen wall in the direction either circular or perpendicular to the sieve axis a rectangular shape, the longitudinal direction being rectangular Recesses in the circumferential direction of the screen or in the direction of Sieve axis can run (see Fig. 6). 5 the embodiment shown in EP-A-0 521 192 forms the Plane-shaped sieve insert plane with the circumferential direction of the sieve an acute angle of 25 ° to 45 °, and rectangular Recesses and thus rectangular sieve inserts form the flanks of the upstream side in the upstream direction Recesses with a circumferential direction Angles from 45 ° to 65 °. The meaning of this well-known construction it is, with seven, which on the upstream side before the Sieve passage channels in the fiber suspension to be sorted Generate turbulence provided with the sieve passage channels Easy to change areas of the screen when these areas are not subject to wear due to their sorting function can do more.

It should also be mentioned that in a sieve according to the invention Sieve passage channels not necessarily exactly in the groove bottom, d. H. in the tip of the approximately V-shaped groove cross section must, but also somewhat upstream relative to the groove base can be offset, d. H. in the lower quarter or lower Third of the front groove side wall can open without thereby greater disadvantages have to be accepted, such as this would be the case if the sieve passage channels in the rear groove side wall would open (risk of clogging the sieve passage channels) or further up in the front Slot side wall would open (shorter service life of the sieve, because then by an abrasive wear the Sieve inflow side the mouths of the sieve passage channels upstream sieve circumference would quickly come closer and thereby Sieve relatively soon to clog its passage channels would tend). The sieve passage channels do not have to arranged exactly one behind the other in the direction of the sieve axis , although this is to be preferred as well as one regarding the sieve axis radial course of the sieve passage channels.

The properties of the sieve according to the invention with regard to the achievable throughput and its operating behavior can be improved more and more, the more the inclination the front groove side wall opposite the wire circumferential direction approximately an angle of approximately 52 ° or approximately 53 ° and an optimum results at an angle of inclination of 52.5 °, especially when the sieve passage is exact flows into the bottom of the groove and flows radially with respect to the sieve axis becomes.

The same applies to the inclination of the rear groove side wall, if namely their angle of inclination with the circumferential direction of the screen an angle of about 20 ° to about 40 °, preferably from about 25 ° to about 35 °, and optimal Properties appear when the rear Groove side wall with the screen circumferential direction an angle of forms about 30 °.

The above applies to the depth of the upstream grooves for the well-known sieve made by Hermann Finckh Maschinenfabrik GmbH & Co. made executions, an optimal value of the groove depth is approximately 1 mm.

With regard to the highest possible strength of the screen wall it is recommended to design the sieve so that - on the Seen upstream side of the sieve - the grooves several, in Sieve circumferential direction extending and in the direction of the sieve axis form rows of grooves spaced from each other.

Although in a sieve with one made from sheet steel Sieve wall the upstream grooves with any known Machining technology could be produced, e.g. B. in that the metal in the area of the grooves to be produced by means of an energy beam (laser or electron beam) is evaporated (the sieve passage channels could also be such energy beam are produced), it is recommended at the current state of the art, for reasons of manufacturing costs and the precision of those to be generated in the screen wall Contours the grooves as created by machining Form wells, so that they are particularly means a milling cutter.

Again, for the sake of the strength of the sieve, it is recommended for such screens, the screen wall of a steel sheet is produced for the screen wall - outside of the upstream side with screen openings connecting the outflow side - a wall thickness of about 6 mm to about 10 mm and in particular from about 6 mm to about 8 mm.

So that the flow resistance for the sorting fineness crucial sieve passage channels as low as possible and so that the achievable throughput is as large as possible, also have preferred embodiments of the invention Siebs as well as a variety of well-known pressure sorter screens wells on their outflow sides, in the each opens at least one sieve passage. Preferably these depressions also have the shape of approximately parallel to the grooves running in the sieve axis.

Further features of preferred embodiments of the invention Siebs can be found in claims 2-27.

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, wobei auch hier das Sieb nur schematisch an-gedeutet wurde;

Fig. 4

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

Fig. 5

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

Fig. 6

einen Schnitt durch eine hinsichtlich der Gestaltung der Siebanström- und der Siebabströmseite bevorzugte Ausführungsform des erfindungsgemäßen Siebs längs einer die Siebachse enthaltenden Durchmesserebene, wobei die Siebdurchlaßkanäle jedoch als Schlitze und nicht als Bohrungen dargestellt und die bei einer Ansicht der Anströmseite des Siebs sichtbaren Details der Einfachheit halber weggelassen wurden;

Fig. 7

den Ausschnitt "X" aus Fig. 6 in größerem Maßstab bzw. einen Schnitt nach der Linie 7-7 in Fig. 8;

Fig. 8

den Ausschnitt "Y" aus Fig. 6 in größerem Maßstab, und

Fig. 9

einen Schnitt durch einen Teil der Siebwand entsprechend der Linie 9-9 in Fig. 8.

Further features, advantages and details of the invention emerge from the appended claims and / or from the following description of particularly advantageous embodiments of the pressure sorter according to the invention and the sieve 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, the sieve also being indicated only schematically here;

Fig. 4

an end view of the rotor, as seen in Figure 1 from the left, including the sieve shown in an axial section.

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;

Fig. 6

a section through a preferred embodiment of the sieve according to the invention along the plane of the diameter containing the sieve inflow and the downstream side of the sieve, the sieve passage channels, however, being shown as slots and not as bores and the details visible in a view of the upstream side of the sieve for the sake of simplicity were omitted;

Fig. 7

the section "X" of Figure 6 on a larger scale or a section along the line 7-7 in Fig. 8.

Fig. 8

the section "Y" of Fig. 6 on a larger scale, and

Fig. 9

8 shows a section through part of the screen wall according to line 9-9 in FIG. 8.

In FIGS. 7-9, the sieve passage channels were also used as Slits drawn; in the sieve according to the invention however, they have the shape of bores, with Fig. 9 on such a sieve applies when the Siebdurchlaßkanäle on Because of the grooves that end according to FIG. 9 of stretch into the sieve wall below.

Regarding the actual pressure sorter shown in FIG. 1 10 with a housing 14 standing on supports 12 still belongs a motor 18 standing on a frame 16, which is is a three-phase or 3-phase AC motor, which by means of a pulley 20 and V-belt 22 a Pulley 24 drives which on a in the frame 16th and the housing 14 rotatably mounted rotor shaft 26 is.

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

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

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

At the right end of the housing 14 according to FIG. 1 there is an inlet connection 46 provided by - as indicated by the arrow F. - The fiber suspension to be processed or sorted is promoted in the pressure sorter, namely by means of a pump, not shown. About in the middle Above the sieve 38 there is an outlet connection 48 on the housing jacket 30 attached, through which the so-called accept material - as by the Arrow A indicated - leaves the pressure sorter. With the accepted material is that part of the fiber suspension which has passed the sieve 38. At the left end according to FIG. 1 the housing shell 30 is finally a second outlet port 50 attached, through which the so-called rejects - as indicated in Fig. 2 by the arrow R - the pressure sorter leaves; the reject is the one Part of the fiber suspension to be processed, which the sieve 38 cannot pass.

Appropriately, you will the inlet port 46 against the Arrange the illustration in Fig. 1 so that the to be sorted Fiber suspension flows approximately tangentially into the housing 14, such as the outlet nozzle 50 for the rejects is aligned tangentially (see Fig. 2). Besides, could the outlet connection 48 of course also at the bottom of the housing jacket 30 be arranged as far as the installation of the pressure sorter 10 allows the discharge of the accepted substance downwards.

Via an inlet connection 46 into the pressure sorter 10 fed fiber suspension to be processed arrives first into an inlet space 52 and then it enters an annular space between the circumference of the rotor 36 and the sieve 38 which will hereinafter be referred to as inlet space 54, namely the fiber suspension to be sorted enters via first axial end 54a of this inlet space in the latter on. As a result of the rotor 36 rotating about the axis 34 and, if necessary, the tangential orientation of the inlet nozzle 46 and due to the pressure under which the to sorting fiber suspension in the pressure sorter 10 promoted the fiber suspension flows helically through the inlet space 54 from its first end 54a to its second end 54b, with part of the fiber suspension passing through Openings of the sieve 38 pass through and thus into the accepted material space 58 arrives. The rejects leave the inlet space 54 the second end 54b and thus reaches the reject space 56, from which the rejects the pressure sorter over the leaves second outlet port 50.

In preferred embodiments of the invention Pressure sorter, the axis 34 extends at least approximately horizontally, but in principle it would also be conceivable that Set up the sorter so that its axis 34 at least runs approximately vertically.

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 adjusting elements could also be provided in the lines 66 and 68, with which the signals supplied by the pressure transmitters 62 and 64 could be changed, so as to make the dependence on the line 76 possible To be able to influence the control signal from the pressure difference mentioned.

3 to 5, the design of the rotor 36 are explained in more detail.

A hub 80 which is fixedly connected to the rotor shaft 26 carries a closed, hollow circular cylindrical rotor body 82 with a circular cylindrical rotor shell 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 carries two sets outside of profile elements, namely a first set, which of Profile elements 86a, 86b, 86c and 86d is formed, as well a second set, formed by profile elements 88a, 88b, 88c and 88d. The first set of profile elements forms one itself in the rotor circumferential direction or direction of rotation U des Rotor's first row of profile elements and in between arranged gaps 86a ', 86b', 86c 'and 86d', and this row defines a first axial rotor section 90, which faces the inlet space 52; the second set of Profile elements 88a-88d form a second, just the same Row of profile elements and gaps arranged between them 88a ', 88b', 88c 'and 88d', and this second row defines a second axial rotor section 92 which is the reject space 56 is adjacent. In the preferred shown Embodiment, all profile elements are of equal height (in Direction of the axis 34 measured), depending on the desired sorting result and / or depending on the type of sorting fiber suspension, however, could be appropriate be to choose the height of the first row larger or smaller than the height of the second row. It can also be useful be to provide the rotor with more than two such rows.

As can be seen in particular from FIGS. 2 and 4, has each profile element one lying in the direction of rotation U at the front End face or first flank I, which is perpendicular to the circular cylindrical Outer peripheral surface of the rotor shell 84 and thus to the area in front of it in the direction of rotation U. Gap runs, as well as a directly on the first edge I. subsequent back surface or second flank II, which against the direction of rotation U in the radial direction to the inside and thus to the axis 34, so that the Profile elements in cross section perpendicular to axis 34 which have a very acute triangle equal, which was bent concentrically to axis 34. With The first flanks I become strong positive in the inlet area 54 Pressure surges and strong turbulence are generated, also with the first flanks I the fiber suspension in the inlet space 54 greatly accelerated, at most up to the rotational speed of the profile elements. On the other hand, the falling ones second flanks II negative pressure pulses through which liquid from the accepted material space 58 through the sieve openings is sucked back into the inlet space 54. Particularly strong Turbulence occurs in the inlet space 54 as a result of the in Direction of rotation U directed flow component of the Fiber suspension when the inside of the screen 38 according to the invention formed "rough", i.e. is profiled.

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, specifically the flanks I are inclined with respect to the direction of the axis 34, so that the direction The flow component of the fiber suspension running along the axis 34 is amplified in the inlet space 54 in the direction from the first axial end 54a of the inlet space to its second axial end 54b.

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 54b. 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 I 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 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 illustrated preferred embodiment, the Lengths of the profile elements of the first row are approximately equal to the lengths of the gaps in the first row, the lengths of the Profile elements of the second row are larger than the lengths the profile elements of the first row, and the lengths of the Gaps in the second row are smaller than the lengths of the Profile elements of the second row and smaller than the lengths the gaps in the first row.

Due to the arrangement of the profile elements of the two Rows result in levels 90, through which the following Effect is achieved: accumulations of fibers and impurities, which are on the first flanks I of the profile elements 86a - 86d of the first row can slide due to the axial flow component of the fiber suspension in the inlet space 54 the first flanks I of the profile elements along the first row towards the second axial end 54b of the inlet space 54 and thus reach the steps 90, in their area due to the strong prevailing there Turbulence resolved and mixed with the fiber suspension - accumulation 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 get into the rejects room 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 peripheral speeds achieved by adjusting the rotor speed the rotor are expediently between about 10 m / s and about 40 m / s, generally the best sorting results with circumferential speeds of approximately 15 to about 30 m / s can be reached.

The structure of the profile elements results from FIGS. 3 and 4 86a-86d and 88a-88d of the preferred shown Embodiment. Each of these profile elements exists - sees one looks from the rotor jacket 84 - the first flank from one I forming bar 100, one forming the second flank II curved sheet 102 and two side walls 104, with respect 3 should be noted that in this Figure because of the oblique course of the first flanks I and so that the last 100 bars not perpendicular to theirs Longitudinal extension, but were cut at an angle to it. Those of the rotor jacket 84, the strips 100, the sheets 102 and the side walls 104 enclosed cavities 106 of the profile elements should be liquid tight or with a filler, such as. a foam plastic, to be filled in to avoid the creation of imbalances in the rotor. Same thing 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.

As can be seen in FIGS. 6 and 8, there are 300 in the wall of the screen 38 around the screen axis 34 a plurality of rows 302 (6 rows in the illustrated embodiment) of screen openings 38a formed between which annular webs 304 are provided, in the areas of which the screen wall 300 has neither screen openings nor a surface profile. How a comparison of FIG. 6 with FIG. 1 reveals forms the inner surface of the circular cylindrical, concentric to the axis 34 Siebs 38 whose upstream side 306, its outer surface the downstream side 308 of the sieve.

Using FIGS. 7-9 and in particular using FIG. 9 the design and arrangement of the screen openings 38a are explained in more detail, being for a simpler drawing 9 shows the screen wall 300 in a flat, level manner Condition was drawn, e.g. B. in that state in which is made of stainless steel sheet Screen wall 300 during processing and before bending as well Welding to a circular cylinder. Show however Figures 7 - 9 slot-shaped sieve passage channels instead Sieve passage channels designed according to the invention as bores.

In the illustrated embodiment of the invention Siebs are each of the sieve openings 38a in cross section to the Sieve axis consisting of four components, which are partially mutually exclusive overlap, namely from three grooves and a sieve passage. The sheet forming the sieve wall 300 was used for each sieve opening 38a from the inflow side 306 an inlet side Milled groove 400, from the downstream side 308 forth first an inner groove 402 and then an outer groove 404, the opening angle of which is greater than that of inner groove 402. Sieve passage channels 406 were then in the Screen wall 300 incorporated, which grooves 400 and 402 together connect. The different components of each Sieve opening 38a are arranged relative to one another in such a way that after bending the screen wall 300 to the circular cylindrical Sieve 38 all on one containing the sieve axis 34 Diameter plane 408 lie - this diameter plane thus represents the central plane of the screen passage 406, likewise the center planes of the grooves 402 and 404, which too this diameter plane 408 are symmetrical, and finally, the bottom of the groove 400 also lies on the diameter plane 408.

In the illustrated preferred embodiment of the invention Siebs is approximately the total thickness of the sieve wall 6 mm, the one measured perpendicular to the inflow side 306 The depth of the groove 400 is 1 mm, the distance between the just formed Bottom of the groove 402 from the downstream side is 308 4 mm, and the groove 404 should be 0.72 mm deep. The opening angle (measured in the plane of the drawing of Fig. 9) of the inner Groove 402 should be 16 °, that of outer groove 404 120 °. It follows from this that 308 is measured on the outflow side the width of the measured in the circumferential direction of the sieve outer groove 404 is 2.5 mm. The diameter of the as Drilled through-hole channels 406 depend on the desired sieve fineness.

In Fig. 9, the direction of rotation of the rotor 36 labeled "U", and in that direction it has Sieve on its upstream side 306 between two successive Grooves 400 each have a surface area 410, which with the sieve wall 300 bent into a circular cylinder Is part of a circular cylindrical surface and its or rotor direction of rotation U measured at shown preferred embodiment 0.5 mm should (generally about 20% to 30% of the maximum width of the Grooves 400).

According to the invention now each of the grooves 400 has a steeper front groove side wall 400a and 400b, a flat extending rear groove side wall, which in the illustrated preferred embodiment form an angle of 97.5 °, while the angle a between the front groove side wall 400a and the diametral plane 408 37 , 5 °, the angle β between the diameter plane 408 and the rear groove side wall 400b is 60 °. With a depth of the groove 400 of 1 mm, this results in a width of the groove 400 of 2.5 mm, measured in the direction of rotation U of the rotor. The angle by which the front groove side wall 400a is inclined with respect to the wire circumferential direction or the rotor rotation direction U is consequently 52.5 °, the angle of inclination of the rear groove side wall 400b with respect to the wire circumferential direction is 30 °.

The "boat-shaped" shape of the grooves that can be seen in FIG. 8 400 (the same applies to the other grooves 404 and 402) just a consequence of the way the grooves are made circular disk-shaped milling cutter and for the function of the sieve according to the invention at least essentially irrelevant.

Since the rotor 36 leads to the still to be sorted Fiber suspension on the upstream side 306 of the sieve 38 in flows substantially in the circumferential direction of the sieve, lead the relatively steep front groove side walls 400a to that generates relatively strong turbulence in the grooves 400 in the vicinity of the front groove side walls 400a a certain negative pressure arises and the essentially Fiber suspension flowing in the direction of rotation U of the rotor is sucked into the grooves 400; on the rear groove side walls 400b impinging parts of the fiber suspension flow through these groove side walls 400b into the inlet space 54 "reflected back", i.e. H. into the the Screen inflow side 306 adjacent circumferential fiber suspension deflected into it and thus prevent it from being sorted in the Fiber suspension adjacent the upstream side 306 of the sieve, reducing the throughput of the pressure sorter Can form nonwoven. As described above that is to be sorted in the inlet space 54 Prevailing static pressure is greater than fiber suspension the static pressure in the accept material space 58, already leads the Pressure drop across the screen wall 300 causes that part the fiber suspension to be sorted, which the sieve passage channels 406 can happen from the upstream side 306 in flows through the sieve passage channels; this process is through generated by the rotor 36 in the fiber suspension to be sorted positive pressure surges supported. On the other hand, they lead negative pressure surges generated by the rotor 36 so that by liquid is drawn back through the sieve passages 406 will, d. H. sucked back from the downstream side 308 to the upstream side 306 , thereby flushing the sieve passages 406 be so that they don't sort through in the Fiber suspension contains fibers, fiber aggregates and Contaminants can become blocked.

Each of the upstream grooves 400 is with the downstream side Grooves 402 and 404 connected via several bores 406, which in the direction perpendicular to the plane of the drawing in FIG. 9 lie in a row.

As can be seen from the dimensions of the screen shown in FIG. 9 shown above, this has a pitch of 3 mm compared to a pitch of 4 mm of a screen, which differs from the screen shown in FIG. 9 only in that not only the angle β, but also the angle a is 60 °, the opening angle of the grooves 400 is 120 °. However, the smaller division results in an approximately 1/3 larger free passage area of the sieve, and surprisingly, a sieve according to the invention leads to an increase in throughput rate at least in proportion to the increase in the free passage area, even though the front groove side walls 400a are steeper than in the previous case Described known sieve from the company Hermann Finckh Maschinenfabrik GmbH & Co. with upstream grooves with a diameter of 408 and an opening angle of 120 °.

The diameter of the sieve passage channels designed as bores 406 of the sieve 38 is expediently about 1 mm to about 3.5 mm when the rotor with a peripheral speed is operated from approx. 10 to approx. 15 m / s. At higher Peripheral speeds can use smaller holes become; expediently one operates according to the invention Pressure sorter with circumferential rotor speeds of approx. 15 to approx. 40 m / s and then selects for the screen openings Bores with a diameter of approx. 0.5 to approx. 1.5 mm.

Claims (28)

1. Screen (38) for sorting fibre suspensions designed so as to be rotationally symmetrical in relation to a screen axis (34) and having an inflow side (306) for the fibre suspension to be sorted and an outflow side (308) opposite thereto, for pressure sorters having a rotor (36) which is rotationally drivable around the screen axis and has profiled elements (86a - d, 88a - d) rotating adjacent to the inflow side (306) of this screen in order to generate positive and negative pressure pulses in the fibre suspension to be sorted, said screen having at its inflow side (306) grooves (400) of approximately V-shaped cross section extending approximately parallel to the screen axis (34) and following each other in the circumferential direction (U) of the screen, with a screen through-channel (406) opening into each of the grooves, each of the grooves (400) being delimited - seen in the direction of rotation (U) of the profiled elements - by a front and a rear groove side wall (400a, 400b) and having a groove base, said screen through-channel (406) opening at least approximately into the groove base, and the front groove side wall (400a) being inclined to a greater extent in relation to the circumferential direction (U) of the screen than the rear groove side wall (400b), and an essentially smooth surface area (410) at least approximately parallel to the circumferential direction being provided in the circumferential direction (U) of the screen between consecutive grooves (400) at the inflow side (306) of the screen (38), characterized in that

   (a) in cross section at right angles to the screen axis (34) the front groove side wall (400a) forms with the circumferential direction (U) of the screen an angle (90° - α) of approximately 40° to approximately 70°;

   (b) in cross section at right angles to the screen axis (34) the two groove side walls (400a, 400b) form with one another an angle (α + β) of approximately 80° to approximately 110°,

   (c) - measured in the circumferential direction (U) of the screen - the width of the surface areas (410) is approximately 20 % to approximately 30 % of the width of the grooves, and in that

   (d) several screen through-channels (406) open into each of the grooves (440), said screen through-channels lying behind one another in the longitudinal direction of the grooves and having the shape of bores.
2. Screen as defined in claim 1, characterized in that the front groove side wall (400a) forms with the circumferential direction (U) of the screen an angle of approximately 45° to approximately 60°.
3. Screen as defined in claim 2, characterized in that the front groove side wall (400a) forms with the circumferential direction (U) of the screen an angle of approximately 50° to approximately 55°.
4. Screen as defined in claim 3, characterized in that the front groove side wall (400a) forms with the circumferential direction (U) of the screen an angle of approximately 52° to approximately 53°.
5. Screen as defined in any one or several of the preceding claims, characterized in that the rear groove side wall (400b) forms with the circumferential direction (U) of the screen an angle of approximately 20° to approximately 40°.
6. Screen as defined in claim 5, characterized in that the rear groove side wall (400b) forms with the circumferential direction (U) of the screen an angle of approximately 25° to approximately 35°.
7. Screen as defined in claim 6, characterized in that the rear groove side wall (400b) forms with the circumferential direction (U) of the screen an angle of approximately 30°.
8. Screen as defined in any one or several of the preceding claims, characterized in that the angle between the two groove side walls (400a, 400b) is approximately 90° to approximately 105°.
9. Screen as defined in claim 8, characterized in that the angle between the two groove side walls (400a, 400b) is approximately 95° to approximately 100°.
10. Screen as defined in claim 9, characterized in that the angle between the two groove side walls (400a, 400b) is approximately 97° to approximately 98°.
11. Screen as defined in any one or several of the preceding claims, characterized in that - in cross section at right angles to the screen axis (34) - a centre of the opening of the screen through-channel (406) facing the inflow side (306) is located at least approximately in the point of intersection of the two groove side walls (400a, 400b).
12. Screen as defined in any one or several of the preceding claims, characterized in that the screen through-channel (406) - in cross section at right angles to the screen axis (34) and in relation to the latter - extends approximately in the radial direction.
13. Screen as defined in any one or several of the preceding claims, characterized in that - measured in the radial direction in relation to the screen axis (34) - the depth of the groove (400) is approximately 0.8 mm to approximately 1.2 mm.
14. Screen as defined in claim 13, characterized in that the groove depth is approximately 0.8 mm to approximately 1 mm.
15. Screen as defined in claim 14, characterized in that the groove depth is approximately 1 mm.
16. Screen as defined in any one or several of the preceding claims, characterized in that the width of the surface area (410) is approximately equal to 1/5 of the groove width.
17. Screen as defined in any one or several of the preceding claims, characterized in that the grooves (400) and screen through-channels (406) are formed in a screen wall (300) which is rotationally symmetrical in relation to the screen axis (34) and is made from a stainless steel sheet.
18. Screen as defined in any one or several of the preceding claims, characterized in that - viewed towards the inflow side (306) of the screen (38) - the grooves (400) form several rows (302) of grooves extending in the circumferential direction (U) of the screen and arranged in spaced relation to one another in the direction of the screen axis (34).
19. Screen as defined in claim 17 or 18, characterized in that the grooves (400) are designed as recesses produced by a cutting process.
20. Screen as defined in any one or several of claims 17 - 19, characterized in that the screen wall (300) has a wall thickness of approximately 6 mm to approximately 10 mm outside screen openings (400, 406, 402, 404) connecting the inflow side (306) with the outflow side (308).
21. Screen as defined in any one or several of the preceding claims, characterized in that the screen (38) has recesses (402, 404) at its outflow side (308) and at least one screen through-channel (406) opens into each of the recesses.
22. Screen as defined in claim 21, characterized in that the recesses (402, 404) have the shape of grooves (402, 404) extending approximately parallel to the screen axis (34).
23. Screen as defined in claim 21 or 22, characterized in that in each plane at right angles to the screen axis (34) only one single screen through-channel (406) opens into each recess (402, 404).
24. Screen as defined in any one or several of the preceding claims, characterized in that in each plane at right angles to the screen axis (34) only one single screen through-channel (406) opens into each of the grooves (400) lying at the inflow side (306) of the screen (38).
25. Screen as defined in any one or several of the preceding claims, characterized in that the bores forming the screen through-channels (406) have a diameter of approximately 0.5 mm to approximately 3.5 mm.
26. Screen as defined in claim 25, characterized in that the diameter of the bores for pressure sorters with a rotor circumferential speed of approximately 10 to approximately 15 m/s is from approximately 1 mm to approximately 3.5 mm.
27. Screen as defined in claim 25, characterized in that the diameter of the bores for pressure sorters with a rotor circumferential speed of approximately 15 to approximately 40 m/s is from approximately 0.5 mm to approximately 1.5 mm.
28. Pressure sorter for fibre suspensions, in particular, for the processing of fibre suspensions recovered from waste paper, comprising a housing (14) having arranged therein a stationary screen (38) which is rotationally symmetrical in relation to a screen axis (34) and separates in the housing a supply chamber (54) enclosed by the screen from an accepts chamber (58) located outside the screen, and a rotor (36) drivable around the screen axis (34) by a motor (18), the circumferential surface of said rotor together with an inflow side (306) 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 of the supply chamber, and a rejects outlet (50) communicating with a second axial end of the supply chamber, wherein in order to generate positive and negative pressure pulses in the fibre suspension there are provided at the circumferential surface of the rotor (36) profiled elements (86a - d, 88a - d) which extend in the circumferential direction of the rotor and each have a first flank (I) lying in front in the rotational direction (U) for driving the fibre suspension in the rotational direction and a second flank (II) located behind the first flank in the direction opposite to the rotational direction for drawing liquid back from the accepts chamber through the screen into the supply chamber, characterized by a screen (38) as defined in any one or several of claims 1 to 27.

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