EP0410102B1 - Straining apparatus - Google Patents

Abstract

The rotor of a sorter has a circumference which, in cross section perpendicular to the rotor axis of rotation, is essentially composed of circular arcs. Depending on sorter size, the number of circular arcs amounts to between two and eight. The eccentricity of the circular arcs relative to their center, based on the rotor axis of rotation, amounts to preferably between 4 and 10 mm. This makes it possible to obtain slight rotor stresses at a good sorting efficacy, preferably also with a mean substance density of more than 3% of fiber suspensions. The difference between the smallest and greatest rotor spacing e=fmax-fmin amounts to maximally 60 mm, preferably 20 mm.

Description

The invention relates to a sorter according to the preamble of claim 1. Such a sorter is known from US-A-3 680 696. Here, the circular arcs arranged offset from one another alone form the rotor contour without a transition piece in between. This leads to a relatively weak pressure pulse and the embodiments are limited to only two circular arcs offset from one another, which form the rotor cross section. This means that there are only two pulses per revolution, which is disadvantageous for large diameter rotors.

Sorters with such sieve baskets essentially have the task of removing disruptive components of fiber suspensions, e.g. to remove light, floating impurities, such as plastic films and the like, heavy components, such as sand, broken glass, pieces of wood and iron parts of an essentially small type, such as paper clips, pieces of wire and the like. This takes place in that, by suitable dimensioning of the perforation of the sieve or the slot width of the sieve or sieve basket, only the good fibers or fiber bundles as far as possible enter an accepting material space.

• 1. Es muß zu einer Erzeugung von Scherkräften und Aufrechterhaltung zu einer turbulenten Bewegung in der Suspension kommen, um die Bildung von Faserflocken, inbesondere bei Feststoffkonzentrationen von mehr als 0,8 %, und eine Entmischung der Suspension in Fasern und Wasser am Sieb, zu verhindern. Im letzteren Fall würde es zu einer Eindickung am Sieb kommen, wodurch der Durchtritt von weiterem Gutstoff durch die Sieböffnungen verhindert werden würde.
• 2. Die Erzeugung von Druckpulsationen am Sieb, um auftretende Verstopfungen der Sieböffnungen durch z.B. Faserflocken und Fremdkörper zu beseitigen bzw. zu verhindern.

For a good sorting efficiency, the following conditions have to be fulfilled:

• 1. Shear forces must be generated and turbulent movement in the suspension must be maintained in order to prevent the formation of fiber flakes, in particular at solids concentrations of more than 0.8%, and segregation of the suspension in fibers and water on the sieve prevent. In the latter case, there would be a thickening on the screen, which would prevent further accept material from passing through the screen openings.
• 2. The generation of pressure pulsations on the sieve in order to eliminate or prevent blockages in the sieve openings, for example by fiber flakes and foreign bodies.

Attempts have recently been made to carry out the sorting process at the highest possible substance concentrations, so that novel rotors have been developed, an example of which is the arrangement according to US Pat. No. 4,200,537. Such rotors have a good sorting efficiency, but put a lot of strain on the screen basket.

The object of the invention is to provide a rotor which, with good sorting efficiency, causes only slight strain on the screen basket.

This object is achieved by the features of the characterizing part of patent claim 1.

According to the invention, it has been recognized that such a rotor generates relatively "gentle" pulsations which run in the form of a gentle wave train.

Fig. 1

einen prinzipiellen Längsschnitt und

Fig. 2

einen Querschnitt dazu und

Fig. 3

einen weiteren Querschnitt einer anderen Ausführungsform

zeigen.The invention is explained below using exemplary embodiments, wherein

Fig. 1

a basic longitudinal section and

Fig. 2

a cross-section of this and

Fig. 3

another cross section of another embodiment

demonstrate.

In Fig. 1, the screen basket is designated 1 and the rotor 2. The suspension is fed into the housing 3 via the inlet connection 5, and the sorted-out waste material is discharged from the waste-material chamber 6 through outlet connection 8 and the remainder of the suspension is removed via connecting piece 9. The rotor drive is indicated at 12, which drives the rotor via the shaft 11 outlined.

According to FIG. 2, the circumference of the rotor 2 is composed in cross section, that is to say in sections perpendicular to the rotor axis or rotor shaft 11, from circular arcs with the radius R _r , which are connected to one another here by a straight connecting piece. This results in an eccentricity E of the center M of the rotor arcs in relation to the rotor axis of rotation M₀. In the middle of the arcs there is a minimum gap of f _min with respect to the screen basket 1 and in the half-angle range between two adjacent minimum gaps f _min there is the maximum gap f _max . The difference between these two columns is indicated by e.

The output rotor, for example a series, for a certain small sorter size with the sieving radius R _s1 is - as shown - formed with two arcs, so that n 1 = 2.

. Es gelten ferner die Beziehungen

${\text{R}}_{\text{r}}{\text{=R}}_{\text{s}}{\text{-f}}_{\text{min}}{\text{-e, wobei E=e/(1-cos a), e=f}}_{\text{max}}{\text{-f}}_{\text{min}}\text{,}$

dabei ist der Winkel a der halbe Winkelabstand zwischen zwei benachbarten Punkten des Rotorumfangs mit dem geringsten Siebabstand f_min; an dieser Stelle liegt dann der maximale Abstand des Rotorumfanges zum Siebkorb 1 f_max. Für diesen Winkel a gilt dann $\text{a=360°/2n}$

.For larger radii R _{s of} the strainer, the following relationship applies to the number (whole number) of arcs ${\text{n = n 1 · R}}_{\text{s}}{\text{/ R}}_{\text{s1}}$

. The relationships also apply

${\text{R}}_{\text{r}}{\text{= R}}_{\text{s}}{\text{-f}}_{\text{min}}{\text{-e, where E = e / (1-cos a), e = f}}_{\text{Max}}{\text{-f}}_{\text{min}}\text{,}$

the angle a is half the angular distance between two adjacent points of the rotor circumference with the smallest sieve distance f _min ; at this point the maximum distance of the rotor circumference to the screen basket is 1 f _max . Then for this angle a applies $\text{a = 360 ° / 2n}$

.

A value in the range between 15 and 45 mm should preferably be selected for the value f _min . The eccentricity E is preferably between 4 and 10 mm.

Such a rotor according to the invention can attain a maximum rotational speed of 1400 rpm with a sieve diameter of 500 mm, which corresponds to a peripheral speed of approximately 35 m / s. There is a good sorting effect with low power consumption of the rotor. The strainer strain is relatively small.

3 also shows the cross section of a rotor according to the invention, the circumference of which is composed essentially of three circular arcs spaced apart at equal angular intervals.

You can also - as shown in solid lines - connect the arcs by straight lines, which preferably run parallel to the common tangent of adjacent arcs.

Overall, there is the advantage of low energy consumption at a high peripheral speed, which is well suited for the fluidization of substances of medium consistency at more than 3%.

Rotors with two to four circular arcs forming the circumference of the rotor are preferably used. Of course, this depends on the size of the sorter or the diameter of the screen basket.

beträgt zwischen 5 und 20 mm. Damit zeichnet sich der Rotor durch eine hinsichtlich eines festen Bezugsortes flach ondulierende Oberfläche aus, die mit hoher Drehzahl bzw. Geschwindigkeit am Siebkorb vorbeibewegt wird. Dabei ist f_max der theoretische maximale Abstand der gemeinsamen Tangente benachbarter Kreisbögen; in diesem Bereich, also an der Stelle des halben Winkelabstandes der Stellen mit dem geringsten Rotorabstand, kann der wirkliche Abstand f_max etwa höchstens 15 % größer sein, z.B. dort die Rotoroberfläche einer gemeinsamen Sekante entsprechend ausgebildet sind. Auch bogenförmige, konkave Verbindungsstücke zwischen den Kreisbögen (Zylinderabschnitten) und eine Annäherung insgesamt durch eine Ellipse (für den Rotor mit zwei Kreisbögen bzw. Zylinderabschnitten) kommen in Frage, mit einer Abweichung vom theoretischen Kreisradius R_r von höchstens 10 %.The value for ${\text{e = f}}_{\text{Max}}{\text{-f}}_{\text{min}}$

is between 5 and 20 mm. The rotor is characterized by a flat undulating surface with respect to a fixed reference point, which is moved past the screen basket at high speed or speed. Here f _{max is} the theoretical maximum distance of the common tangent of neighboring arcs; in this area, i.e. at the point of half the angular distance of the points with the smallest rotor distance, the actual distance f _{max may be} about 15% greater, for example, where the rotor surface is designed to correspond to a common secant. Arc-shaped, concave connecting pieces between the circular arcs (cylinder sections) and an overall approximation by an ellipse (for the rotor with two circular arches or cylinder sections) are also possible, with a deviation from the theoretical circular radius R _r of at most 10%.

betragen.The actual maximum distance of the rotor surface from the screen basket 1 should be at most 1.15f _max - i.e. 1.15 times the theoretical maximum distance f _max if the rotor contour consists of arcs and common tangents of adjacent arcs (or cylinder sections and tangential, flat planes) connecting them Surfaces) is formed, - preferably ${\text{(1 + 0.2 / n) f}}_{\text{Max}}$

be.

The base radius R _s1 - for a screen basket or sorter with minimal dimensions - is approximately 250 - 270 mm.

Claims (3)

1. A grader having a rotationally-symmetrical sieve basket (1) and a coaxial rotor (2) arranged radially inwardly thereto, the periphery of the rotor in any cross-section at right-angles to the axis of rotation (M₀) of the rotor being at least predominantly formed of mutually regularly angularly-offset arcs of circles of the same radius (R_r), which is smaller than the inner radius (R_s) of the sieve basket (1), characterised in that the formula ${\text{R}}_{\text{r}}{\text{= R}}_{\text{s}}{\text{-f}}_{\text{max}}$

   

   applies for the arcs of circles, f_min being the minimum distance of the periphery of the rotor from the sieve basket (1) and f_max being the theoretically maximum distance of the periphery of the rotor from the sieve basket (1) as the maximum distance of the common tangent of adjacent arcs from the sieve basket (1) and in this region f'_max is the actual maximum distance of the periphery of the rotor from the sieve basket, if it is not designed there running according to the common tangent, and which is at most equal to 1.15·f_max, the distance between f_min and f'_max increasing substantially constantly and a maximum deviation of the radius R_r of 5% of the value as given according to the formula in the form of an elliptical or similar rotor contour being permissible, and the transition of the contour between the arcs is designed as a common tangent or secant of adjacent arcs or is concave and arcuate, and that furthermore the difference ${\text{e = f}}_{\text{max}}{\text{-f}}_{\text{min}}$

   

   is at most 60 mm and f_min is between 15 and 45 mm and E is between 5 and 100 mm, with $\text{a = 360°/2n}$

   

   

   , $\text{E = e/(1-cos a)}$

   

   , if the angle a is equal to half the angular distance of two rotor contour points which are adjacent in the peripheral direction of the rotor with the minimum distance f_min from the sieve basket (1) and if E is the offset of the centre point M of the rotor arcs from the axis of rotation of the rotor M₀, ${\text{e = f}}_{\text{max}}{\text{-f}}_{\text{min}}$

   

   

   and n is equal to the number of arcs of each rotor cross-section.
2. A grader according to Claim 1, characterised in that the value of ${\text{e=f}}_{\text{max}}{\text{-f}}_{\text{min}}$

   

   is between 5 and 20 mm.
3. A grader according to one of Claims 1 or 2, characterised in that the actual maximum distance of the rotor surface from the sieve basket (1) f'_max is at most equal to ${\text{(1+0,2/n)·f}}_{\text{max}}$

   

   , and that ${\text{n = n₁·R}}_{\text{s}}{\text{/R}}_{\text{s1}}$

   

   for n, and n₁=2 applies for a rotor to be given minimum dimensions corresponding to a low grader size with the sieve radius R_s1.

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