EP3628411B1 - Screen star for a screening device - Google Patents

Description

The invention relates to a screening star for a screening device for screening material to be screened. The invention also relates to a screening device with a plurality of shafts which are rotatably arranged next to one another and on which the screen stars according to the invention are arranged axially next to one another in such a way that the screen stars of adjacent shafts engage in one another in the manner of a comb. The material to be screened can be bulk material, in particular mixtures containing soil, such as field crops covered with soil, compost, bark mulch, peat and the like or, for example, building rubble.

Star screens and screening devices, so-called star screens, as the invention relates, among other things, are from EP 1 088 599 B1 and the EP 2 666 549 B1 known. These screening devices and screening stars have proven themselves for screening the materials to be screened. With screening devices of this type, however, cohesive components of the material to be screened, such as loamy and moist soil, first settle on the backs and in the foot areas of the sickle-shaped fingers and, starting from these spaces, also cover the facing, lateral faces of the screening stars. The so-called disc formation occurs. The screening effect suffers as a result, and the drive power to be applied increases. The electric drive draws more power. Eventually, the screening device may become clogged and the drive may switch off due to overload.

the DE 195 00 022 A1 discloses a screening device for screening bulk materials that are difficult to screen. The screening device consists of several parallel, driven shafts on which non-rotatable screen star disks with elastically flexible fingers are arranged. Two of the mirror-symmetrical, truncated cone-like screen star disks are joined together at their two large truncated cone bases and thereby form a screen star, so that several screen stars are arranged next to one another on each screen shaft in a rotationally fixed manner.

In the EP 2 181 575 A1 describes star wheels for star wheel rollers of conveyor or trend devices. The star wheels, which are essentially made of plastic have star-shaped protruding fingers on one hub part. Furthermore, the star wheels, at least in the area of the fingers, are provided with shaped structures which are predetermined by weight and load-optimized effective parameters.

the US 5,975,441A discloses an apparatus for separating stones from stony material, such as earthen material. The device comprises a number of spiked rollers, each of which has a number of detachable spikes. The detachable spikes are staggered with respect to the spikes of an adjacent spiked roller so that as the spiked roller rotates, each spike can rotate through the gap between two spikes of the adjacent spiked roller and smaller rocks can fall through the gap between the spikes.

An agricultural separator with star shafts, each having a plurality of resilient star wheels is in DE 697 01 393 T2 disclosed. Rings made of resilient material are fitted between the star wheels of the star shafts, which ensure better deformability to facilitate the self-cleaning of the star shaft.

It is therefore an object of the invention to counteract the adhesion of screenings components to the screening star and thus disc formation.

Accordingly, the subject matter of the invention is a screen star for a screening device, which comprises a hub for arranging the screen star on or on a rotatable shaft and a plurality of elastically flexible fingers, which protrude radially outwards from the hub and are distributed in the circumferential direction about an axis of rotation of the screen star. The respective finger extends radially and also in the circumferential direction, for example in the shape of a sickle, up to a free end trailing in the direction of rotation. The fingers can be made of rubber or, in particular, an elastomeric plastic such as a polyurethane (PU) plastic. The rubber or polymer can contain reinforcement particles, for example reinforcement fibers or also larger reinforcement structures, and in principle also other particles to achieve certain material properties. The sieve star is an assembly unit, ie it can be assembled as a unit. Hub and fingers are molded together as a unit, ie not joined from several parts.

According to the invention, the fingers each taper from the foot area in the direction of the free end and in circular-cylindrical sections concentric to the axis of rotation in the circumferential direction on at least one face. When they taper towards the free end, the fingers taper on both end faces in the longitudinal direction of the fingers. This means that the fingers taper on both end faces in relation to a central cross-sectional plane of the sieve star, i.e. the end faces of the fingers taper at least in sections, preferably over the majority of their length and particularly preferably from the foot area to the respective free end, i.e. over the entire length of the respective finger, are inclined to the central cross-sectional plane. When it is mentioned below that the fingers taper in the longitudinal direction, this fact is expressed in an abbreviated form. A taper in the circumferential direction can in principle only be realized on one end face of the sieve star, but in preferred embodiments the fingers taper in the circumferential direction on both end faces.

The first idea according to the invention, a two-sided taper in the longitudinal direction of the respective finger, causes the meshing star screens of adjacent shafts to no longer form pairs of screen gaps with axially facing, parallel end faces, which promotes disc formation in conventional screening devices. The neighboring screen stars, which each form a lateral screen gap with each other, only come closest to each other via the lateral screen gap along a line or a narrow strip and no longer over the entire surface. The space laterally between the axially adjacent screen stars widens from a narrowest, linear or at most strip-shaped screen gap in the circumferential direction. The axial, i. H. Pressing forces exerted laterally on the material to be screened decrease from the linear screen gap in the circumferential direction of the screen stars. Cohesive or other components of the material to be screened are no longer rubbed or ground to a large extent on the mutually facing end faces of the screen stars.

The second idea according to the invention, a tapering in the circumferential direction on at least one end face, has the result that the meshing star screens of adjacent shafts come closest to each other in the area of their axially facing end faces only linearly or in the area of a narrow strip, but no longer over the entire surface. This applies when the fingers each have only one taper in the circumferential direction. On the other hand, if the fingers are tapered both in the longitudinal direction of the fingers and in the circumferential direction there are only punctiform constrictions, ie the space laterally between the axially adjacent sieve stars widens from one or possibly two punctiform constrictions in the circumferential direction. The pressing forces exerted axially on the material to be screened by adjacent screening stars decrease starting from the punctiform constriction(s). The adhesion of cohesive screenings components and thus the formation of discs is counteracted even more effectively when both types of tapering are superimposed.

When tapering along the fingers, the fingers are designed in such a way that they progressively taper radially outwards in the longitudinal direction of the fingers on both end faces of the sieve star. The adhesion of cohesive material to be screened is thus counteracted on both end faces, for example also when a sieve star which is tapered according to the invention interacts with a simple disk-shaped sieve star on one or optionally also on both end faces. In advantageous embodiments, the fingers taper, starting from their foot regions, in the longitudinal direction of the fingers in each longitudinal section of the finger. In modifications, however, they can also taper only in a circular ring extending around the axis of rotation in the longitudinal direction of the fingers, then preferably starting directly from the foot area and/or up to an enveloping circle of the sieve star.

Expediently, the fingers, which according to the invention taper in circular-cylindrical cuts concentric to the axis of rotation in a circumferential direction on at least one end face, can taper in the circumferential direction on both end faces of the sieve star. In relation to the direction of rotation, the fingers can be tapered in the direction of the front and/or in the direction of the back of the respective finger. A taper in the circumferential direction can be realized over the entire length of the respective finger, ie in all circular-cylindrical sections of the fingers. Instead, the tapering in the circumferential direction can also be realized only in a radially outer end region encompassing the free end or only in the foot region. The fingers can be tapered in the circumferential direction from the front to the back of the respective finger or at least over the majority of their circumferential extent measured in the respective section.

The taper in the longitudinal direction of the fingers and/or the taper in the circumferential direction can be in relation to an axially central cross-sectional plane of the sieve star basically be designed asymmetrically, but the tapering along the fingers and/or the tapering against the direction of rotation preferably takes place symmetrically to the central cross-sectional plane.

In first variants, the fingers taper in the longitudinal direction of the fingers with a constant angle of inclination to a radial cross-sectional plane, in preferred embodiments over the entire extension of the fingers. Accordingly, the end faces each form a conical surface in the tapering area. Accordingly, the lateral screening gaps, i.e. the lateral narrow points, of a screening device equipped with screening stars that are conical on both sides are straight.

Instead, the angle of inclination can also vary in other variants along the fingers. In second variants, the angle of inclination measured on a radial cross-sectional plane can increase on one or advantageously on both end faces in the longitudinal direction of the respective finger towards the free end, so that the fingers are convex in shape on the end face in question. If juxtaposed shafts of a screening device are equipped with screening stars, each of which has convex, preferably outwardly curved, end faces on both end faces, a punctiform constriction is obtained in the space laterally between meshing screening stars. In the top view of such a star screen, the lateral screen gaps widen from the point-like constriction. In third variants, the angle of inclination can decrease outwards on one or advantageously on both end faces in the longitudinal direction of the respective finger, so that the fingers are concavely shaped on the end face in question. In a sieve device, sieve stars with a convex end face on both sides and sieve stars with a concave end face on both sides can mesh in an axially alternating sequence. In such a screening device, first shafts can have, for example, star screens each with convex end faces and second shafts can have star screens each with concave end faces, and the first shafts and the second shafts can be arranged alternately next to one another. The lateral sieve gaps are no longer straight in such a sieve device, so that elongate, slender particles to be sieved can fall through the lateral sieve gaps more or less only in the direction of their longitudinal extension.

The fingers of the sieve star each have a front surface pointing in the direction of rotation on their front side and a rear surface pointing against the direction of rotation on their back side Surface, a left face, a right face, and front and rear transitions. The front transitions, namely a left transition and a right transition, connect the two end faces with the front surface. The rear transitions, namely a left transition and a right transition, connect the two front surfaces with the rear surface.

In a further exemplary embodiment, the front transitions and/or the rear transitions are each curved at a radius of curvature of at least 1.5 mm or at least 2 mm. The transitions are usually edge-shaped, each with a significantly smaller radius of curvature of less than 1 mm. Softly rounded transitions, for example, also counteract the adhesion of cohesive screenings components. Softly rounded rear transitions are particularly advantageous, since the adhesion of material to be screened usually begins on the rear surfaces of the fingers and from there progresses radially outwards and also axially to the sides. Edged, almost right-angled transitions favor the formation of discs, whereas the screenings in the area of the softly rounded transitions are more likely to be carried away by the neighboring sieve star.

The fingers can each have a convex shape on their front side pointing in the direction of rotation and/or on their back side pointing counter to the direction of rotation with respect to the axial direction, for example roundly bulging outwards with respect to the axial direction or be arrow-shaped. This means that the front surface and/or the rear surface of the respective finger is or are convex in the circular-cylindrical sections concentric to the axis of rotation, i.e. the front surface is convex in the direction of rotation and/or the rear surface is or are convex against the direction of rotation. If one of the two surfaces is arrow-shaped, the two flat sides running towards one another in the shape of an arrow advantageously merge into one another in the axially central surface area with a radius of curvature of at least 1.5 mm or at least 2 mm.

Each of the two ideas according to the invention, the tapering in the longitudinal direction of the fingers and the tapering in the circumferential direction, counteracts the adhesion of screening material components on at least one end face. Also the embodiment with softly rounded front and/or rear transitions counteracts the adhesion of screenings components, in particular in combination with the two ideas according to the invention.

In advantageous embodiments, the fingers do not taper off at their free ends, but instead have an end width B _E measured axially of more than 5 mm or more than 7 mm. The end width B _E is preferably in the range of 15 ± 10 mm. With a taper in the longitudinal direction of the finger and a taper in the circumferential direction on at least one end face, the fingers can each be axially narrowest in the area of the free end.

In the foot area, the fingers can have an axially measured foot width B _F of more than 12 mm or more than 15 mm. A foot width B _F in the range of 26 ± 14 mm is preferred. With tapering in the longitudinal direction of the finger and/or tapering in the circumferential direction, the ratio of foot width to end width, B _F /B _E , can be 1.5 or greater, for example, but is at most 2.5 or preferably less in advantageous embodiments.

The gap width of the lateral screen gaps can be determined in particular by an axial overhang of the hub over the foot area of the fingers. Thus, the hub can have a collar running around the axis of rotation, which protrudes over the finger foot area by the axial overhang. Such a collar is expediently present on both end faces. In advantageous embodiments, the overhang of the respective collar is more than 0.5 mm or at least 1 mm; the overhang is preferably selected from the range of 7±6 mm or 7±3 mm.

Advantageous developments of the invention according to claim 1 are also described in the embodiments formulated below.

In a first exemplary embodiment, the fingers each have a rotationally-facing front surface, an anti-rotationally-facing rear surface, an outer left face, an outer right face, front transitions connecting the front surfaces to the front surface, and rear transitions, connecting the end surfaces to the rear surface, the front transitions and/or the rear transitions each being curved at a radius of curvature of at least 1.5 mm or at least 2 mm.

In a further exemplary embodiment, the fingers taper over at least a predominant part of their length, measured from the foot area to the free end, on both end faces in a continuously differentiable manner. In particular, the fingers can each taper in the direction of the free ends in an axial view of an end face of the screen star.

The fingers can progressively taper outwards on both end faces of the screen star in the radial direction.

Irrespective of this, the fingers on both end faces of the screen star can progressively taper outwards in the direction of the free end of the respective finger in relation to a cross-sectional plane of the screen star.

The fingers can progressively taper outwards on both end faces of the sieve star in the direction of the free end of the respective finger without kinks.

In a further exemplary embodiment, the fingers on both end faces of the sieve star taper conically progressively outwards in the direction of the free end of the respective finger with a constant angle of inclination.

In circular-cylindrical sections concentric to the axis of rotation, the fingers can each have a front side pointing in the direction of rotation, a back side pointing counter to the direction of rotation, a left-hand end face and a right-hand end face, with the end faces running towards one another in the circumferential direction over at least the majority of their circumferential extension, so that the fingers in the circular-cylindrical sections each taper in the circumferential direction.

In addition, the fingers in circular-cylindrical sections concentric to the axis of rotation can each have a front side pointing in the direction of rotation, a rear side pointing counter to the direction of rotation, a left-hand end face and a right-hand end face, the end faces in the circular-cylindrical sections converging in the shape of arrows.

In a further exemplary embodiment, the fingers are elongated in a circular or elliptical shape in circular-cylindrical sections concentric to the axis of rotation. Irrespective of this, the fingers can each taper in circular-cylindrical sections concentric to the axis of rotation over at least the predominant part of their circumferential extent in the circumferential direction.

In a further exemplary embodiment, the fingers of the sieve star according to the invention each have a front side pointing in the direction of rotation, a rear side pointing against the direction of rotation, a left end face and a right end face in circular-cylindrical sections concentric to the axis of rotation, and in the circular-cylindrical sections the front side in the direction of rotation and /or the back is or are arrow-shaped against the direction of rotation. The front and/or the back can have a left flat side and a right flat side and the flat sides can converge in the shape of an arrow. In particular, the flat sides are flat or rounded outwards.

In another exemplary embodiment, the fingers each have a rotationally facing front surface, an anti-rotational rear surface, an outer left face, and an outer right surface, with the front and/or the rear surface being or being convex. The front side can be curved outwards in the direction of rotation and/or the back side against the direction of rotation.

In a further development, the hub can consist of a harder material than the fingers, for example a metal material or a harder plastic or rubber material.

In a further exemplary embodiment, the hub and the fingers are each formed from a plastic material, the plastic material being filled with an additive which reduces fretting in the region of the free ends of the fingers.

Advantageously, the fingers are made of an elastomeric plastics or rubber material optionally filled with reinforcing material.

The fingers of the sieve star according to the invention advantageously have a width B _F axially in a foot area and a width B _E at the free end, with B _F /B _E being at least 1.5 and at most 2.5, preferably 1.8±0.2.

The sieve star can have a maximum axial width B _N in the area of the hub and the fingers can have a maximum axial width _BF in the foot area, with B _N /B _F being at least 1.5 and at most 2.5, preferably 1.8±0.3.

Alternatively or additionally, the sieve star can have a maximum axial width B _N in the area of the hub and the fingers can each have a width B _E at the free end, with B _N /B _E being at least 2 and at most 4, preferably 3.2±0.4 .

In an exemplary embodiment, a flight circle of the sieve star or an enveloping circle placed radially on the outside at the free ends of the fingers has a diameter of at least 150 mm and at most 300 mm, preferably 190±40 mm.

A finger foot circle of the screen star or an outer circumference of the hub can have a diameter of at least 50 mm and at most 200 mm, preferably 100±30 mm.

In an exemplary embodiment, the hub on both end faces of the sieve star has a collar around the axis of rotation of the sieve star, which protrudes axially by at least 1 mm and at most 12 mm, preferably 7±3 mm, over the fingers.

The hub of the screen star may have a central axial passage with a non-circular cross-section, preferably with at least one flat side, for non-rotating mounting on the shaft.

Further developing embodiments of the screening device according to claim 10 are described below.

In a first exemplary embodiment of the screening device, a radial gap width over an axial length of the respective frontal screening gap is at least 2 mm and at most 12 mm, preferably 6±2 mm. A lateral gap width can be along the respective lateral screen gap everywhere at least 1 mm and at most 10 mm, preferably 4 ± 2 mm.

In a further exemplary embodiment, the screening device comprises a drive device for driving the shafts in rotation, with the drive device being set up to drive adjacent shafts at the same speed.

Irrespective of this, the screening device can comprise a drive device for rotating the shafts, the drive device being set up to vary the speed of at least one of the shafts during operation of the device relative to the speed of an adjacent shaft.

Figur 1

einen beispielhaften und im Stand der Technik bekannten Siebstern eines ersten Ausführungsbeispiels in einer axialen Sicht auf eine Stirnseite, zur Erleichterung des Verständnisses der Erfindung,

Figur 2

den Siebstern in einer perspektivischen Sicht,

Figur 3

den Siebstern im Schnitt A-A der Figur 1,

Figur 4

den Schnitt B-B durch einen Finger des Siebsterns der Figur 1,

Figur 5

den Siebstern in einer radialen Sicht auf den äußeren Umfang,

Figur 6

eine Siebvorrichtung mit aus dem Stand der Technik bekannten Siebsternen in einem Schnitt,

Figur 7

die Siebvorrichtung der Figur 6 in einer axialen Sicht,

Figur 8

eine Draufsicht auf eine Siebfläche einer Siebvorrichtung mit weiteren aus dem Stand der Technik bekannten Siebsternen,

Figur 9

eine Draufsicht auf eine Siebfläche einer Siebvorrichtung mit weiteren aus dem Stand der Technik bekannten Siebsternen,

Figur 10

Formen des Querschnitts B-B der Finger von Siebsternen,

Figur 11

einen erfindungsgemäßen Siebstern in einer axialen Sicht auf eine Stirnseite,

Figur 12

den Siebstern der Figur 11 im Schnitt B-B,

Figur 13

den Schnitt A-A durch einen Finger des Siebsterns der Figur 11,

Figur 14

den Siebstern der Figur 11 in einer perspektivischen Sicht,

Figur 15

alternative Formen des Querschnitts B-B von in Umfangsrichtung verjüngten Fingern von Siebsternen,

Figur 16

zusammenwirkende Siebsterne des ersten Ausführungsbeispiels mit linienförmiger Engstelle im seitlichen Siebspalt,

Figur 17

zusammenwirkende Siebsterne des vierten Ausführungsbeispiels mit punktförmiger Engstelle im seitlichen Siebspalt, und

Figur 18

die Siebsterne der Figur 17 in veränderter Drehposition.

Exemplary embodiments of the invention are explained below with reference to figures. Features that are evident from the figures each individually and also in each non-contradictory combination of features advantageously further develop the subject matter of the claims and also the configurations described above. Show it:

figure 1

an exemplary and in the prior art known sieve star of a first embodiment in an axial view of a front side, to facilitate understanding of the invention,

figure 2

the sieve star in a perspective view,

figure 3

the sieve star in the average AA of the figure 1 ,

figure 4

the cut BB through a finger of the sieve star the figure 1 ,

figure 5

the screen star in a radial view of the outer circumference,

figure 6

a screening device with screening stars known from the prior art in a section,

figure 7

the screening device figure 6 in an axial view,

figure 8

a plan view of a screen surface of a screening device with other screening stars known from the prior art,

figure 9

a plan view of a screen surface of a screening device with other screening stars known from the prior art,

figure 10

Shapes of cross-section BB of fingers of sieve stars,

figure 11

a screen star according to the invention in an axial view of a front side,

figure 12

the sieve star figure 11 on average BB,

figure 13

the cut AA through a finger of the sieve star the figure 11 ,

figure 14

the sieve star figure 11 in a perspective view,

figure 15

alternative shapes of the cross-section BB of circumferentially tapered fingers of sieve stars,

figure 16

cooperating screen stars of the first embodiment with a linear constriction in the lateral screen gap,

figure 17

interacting screen stars of the fourth embodiment with a punctiform constriction in the lateral screen gap, and

figure 18

the sieve stars of figure 17 in a different rotational position.

the Figures 1 and 2 show a screen star 1, as is known from the prior art, in an axial view of an end face and in a perspective view for better understanding of the invention. The sieve star 1 has a hub 2 and a plurality of fingers 5a distributed over the circumference of the hub 2, which protrude outwards from the outer circumference of the hub 2 in the radial direction R, starting from foot areas 6, and in the circumferential direction T and thereby counter to the direction of rotation of the sieve star 1 crescent-shaped bent inward to a free end 7 extend. In the figure 1 The circumferential direction T entered is the direction of rotation of the sieve star 1. In relation to the circumferential and rotational direction T, the free ends 7 are trailing ends.

The term “circumferential direction” covers the direction of rotation and the opposite direction in equal measure, while when using the term “direction of rotation” a distinction is to be made between these two circumferential directions.

The fingers 5a can be bent elastically and are therefore flexible. They are made of a plastic material. The hub 2 can be formed from the same plastic material or from a different, then expediently harder, plastic material. The hub 2 has a passage 3 in the central area for the arrangement on the shaft. The passage 3 is formed as a multi-flat in order to connect the sieve star 1 in a form-fitting manner to the shaft so that it cannot rotate. The hub 2 can have an insert made of a metal material in a central area for a rotationally immovable arrangement on a rotationally drivable shaft. more preferably, however, the plastic in the area of the hub 2 is sufficiently strong and hard so that such an insert can be dispensed with.

As in figure 1 and in particular figure 2 As can be seen, the hub 2 has a collar 4 which protrudes axially over the fingers 5a and runs around a central axis of rotation D of the sieve star 1 . On the other end of the star screen 1, the hub 2 has a collar 4 of the same type. The outer circumference of the collar 4 on both sides is at the same time the outer circumference of the hub 2. The fingers 5a project outwards practically directly from the outer circumference of the collar 4, so that the foot areas 6 of the fingers 5a extend almost to the outer circumference of the hub 2 or the collar 4 enough. To a good approximation, the outer circumference of the collar 4 can be regarded as the circle of the feet of the fingers 5a.

One of the fingers 5a serves as a cleaning finger. A cleaning element 9 made of a metal material is supported on the front side of this cleaning finger 5a. In a screening device with a plurality of shafts arranged next to one another, on which several of the screening stars 1 are arranged axially next to one another and mesh with one another, the cleaning element 9 of the respective screening star 1 acts as a scraper, which removes material adhering to the axially adjacent screening stars 1 and one or the two scrapes adjacent shafts and thereby contributes to the screen gaps not clogging. To increase the rigidity against bending, the cleaning finger 5a is not crescent-shaped, but rather extends at least essentially straight in the radial direction R and counter to the direction of rotation T and, measured in the circumferential direction T, has a greater thickness than the other fingers 5a. Advantageous configurations for the combination of cleaning finger 5a and cleaning element 9 are, for example, in FIG EP 1 088 599 B1 described.

When rotating about the axis of rotation D, the free ends 7 of all fingers 5a and also the free end of the cleaning element 9 revolve around an enveloping circle with the diameter D _H . In the region of the collar 4, the hub 2 has an outer circumference with a diameter D _N which, in the context of the invention, is regarded as the diameter of the root circle of the fingers 5a. The diameter D _H is selected from the range of 150 mm to 250 mm, preferably 150 mm to 230 mm. The diameter _DN is selected from the range of 50 mm to 200 mm, preferably 70 mm to 130 mm. The radial extension of the fingers 5a is from the range of 50 mm to 180 mm, preferably 80 mm to 120 mm. These are just examples of preferred size ranges. The invention is also advantageous for other diameter ranges.

The fingers 5a each have, with respect to the direction of rotation, a front or front surface 10, a rear or rear surface 11, a left face 12 and a right face 13, and connecting transitions 14 at the front 10 and connecting transitions 15 at the rear 11 . The transitions 14 and 15 are softly rounded by connecting the respective end faces 12 and 13 to the front surface 10 and the rear surface 11 with a radius of curvature of 1.5 mm or more, preferably 2 mm or more. By avoiding sharp edges at the respective transition 14 and 15, the adhesion of cohesive screenings components is counteracted.

The fingers 5a and also the cleaning finger 5a each taper progressively from the foot region 6 in the direction of the free end 7, ie they taper in the longitudinal direction L of the respective finger 5a in the cuts CC. This results in favorable conditions with regard to the desired elastic flexibility along the fingers 5a on the one hand with sufficient stability in the respective foot area 6 on the other. The narrowing along the fingers 5a is accompanied by a narrowing also in the radial direction R and thus in the longitudinal sections of the sieve star 1 containing the axis of rotation D. In figure 1 a longitudinal section AA is entered. In circular-cylindrical sections BB concentric to the axis of rotation D, ie in the circumferential direction T, the fingers 5a have a constant width, measured axially, apart from a convexly rounded front end section and a convexly rounded rear end section.

In figure 3 is the sieve star 1 in the section AA of the figure 1 shown. Section AA shows the course of the longitudinal direction of the finger L ( figure 1 ) progressive rejuvenation recognizable. The tapering occurs symmetrically on both end faces in relation to an axially central cross-sectional plane Q. By way of example, the taper is formed in such a way that a symmetrical trapezoid with a radially inner long base in the finger foot region 6 and a comparatively shorter outer base at the free end 7 results in the sections AA for each of the fingers 5a. The two inclined end faces 12 and 13 enclose an acute angle with one another. The fingers 5a taper in the radial direction R directly from the base circle or the base regions 6 to the enveloping circle or the free ends 7. The cross-sectional plane Q forms the bisector. The angle of inclination α measured on it is at least 3° or at least 4° and preferably at most 20° or at most 16°.

In the sections CC extending in the longitudinal direction L of the respective finger 5a, the taper runs over a greater length, but otherwise analogously to the taper in section A-A, so that the end faces 12 and 13 in sections CC are at an angle of inclination that is slightly smaller than the angle α is to run into each other. The end faces 12 and 13 each run along the fingers 5a from the foot area 6 to the free end 7 in a monotonous and continuously differentiable manner. The fingers 5a taper in the longitudinal direction L of the fingers in each length section.

The cleaning finger 5a corresponds to the other fingers 5a in terms of taper. In the exemplary embodiment, the cleaning finger 5a thus tapers in the longitudinal direction of the cleaning finger 5a and radially outwards, each symmetrically to the central cross-sectional plane Q.

figure 4 shows one of the fingers 5a in section BB. As is known in the prior art, the end faces 12 and 13 of the fingers 5a are parallel in the circular-cylindrical sections BB concentric with the axis of rotation D. However, the front surface 10 and the rear surface 11 are convex and curve outwards uniformly and round over the entire width of the respective finger 5a in the respective section BB. As in the exemplary embodiment, they can be bulged with a constant radius. As already explained, the transitions 14 and 15 are not angular but softly rounded, with the respective radius of curvature being smaller than the radius of the surfaces 10 and 11 and advantageously being at least 1.5 mm or 2 mm or more.

figure 5 is a radial view of the outer circumference of the screen star 1 of the first embodiment. It can be seen that the fingers 5a and also the cleaning finger 5a each taper progressively from the foot area 6 in the direction of the free end 7 .

• 1.5 ≤ B_F/B_E ≤ 2.5, vorzugsweise 1.6 ≤ B_F/B_E ≤ 2
• 1.5 ≤ B_N/B_F ≤ 2.5, vorzugsweise 1.5 ≤ B_N/B_F ≤ 2.1
• 2 ≤ B_N/B_E ≤ 4, vorzugsweise 2.8 ≤ B_N/B_E ≤ 3.6

The fingers 5a each have their greatest width, B _N , along the hub 2 , a smaller width, B _F , at the root circle, and the smallest width, B _E , at the free ends 7 . The following ratio ranges are advantageous:

• 1.5 _≤ BF / _BE ≤ 2.5, preferably 1.6 _≤ BF / _BE ≤ 2
• 1.5 ≤ B _N /B _F ≤ 2.5, preferably 1.5 ≤ B _N /B _F ≤ 2.1
• 2 ≤ B _N / _BE ≤ 4, preferably 2.8 ≤ B _N / _BE ≤ 3.6

The hub width B _N is selected from the range of 25 mm to 40 mm, preferably 30 mm to 40 mm. The root circle width B _F is selected from the range of 12 mm to 25 mm, preferably 15 mm to 22 mm. The end width B _E is selected from the range of 5 mm to 20 mm, preferably 7 mm to 15 mm. These are just examples of preferred size ranges. The invention is also advantageous for other width ranges.

the Figures 6 and 7 each show a portion of a screening device with screening stars of the first embodiment. figure 7 shows the partial area in an axial view of one end face of the sieve stars 1. figure 6 shows the same section in section EE figure 7 , in which the axes of rotation of the shafts 20 extend.

The screening device has a plurality of rotationally drivable shafts 20 which are arranged next to one another and along which a plurality of screening stars 1 are arranged next to one another. The sieve stars 1 are mounted on the shafts 20 and secured against rotation. The sieve stars 1 of adjacent shafts 20 engage with each other with their fingers 5a in the manner of a comb, so that the sieve stars 1 of one shaft 20 and the sieve stars 1 of the adjacent shaft 20 alternately form lateral sieve gaps 21 and frontal sieve gaps 22 in the longitudinal direction of the shaft, which in plan view are common result in a coherent screen gap 21, 22 which meanders in the axial direction. The mutually facing end faces of intermeshing star screens 1 delimit the lateral sieve gaps 21. The free ends 7 of the sieve stars 1 delimit the frontal sieve gaps 22 with the radially facing, outer peripheral surfaces of the collars 4 of the sieve stars 1 of the respectively adjacent shaft 20.

The lateral screen gaps 21 each have a narrowest screen gap, strip-shaped in section EE, with a gap width Ws, corresponding to the conical taper of the screen stars 1 . The narrowest screen gap is linear in the circumferential direction of the screen stars 1 . The front screen gaps 22 each have between the free end 7 and the outer Circumferential surface of the two collars 4 a narrowest screen gap with a radial gap width W _R on. The gap widths W _R and Ws largely determine the fineness of the star screen formed by the screen stars 1 . Due to the tapering in the longitudinal direction of the fingers 5a, the axial length of the frontal screen gaps 22 is reduced in comparison to simply disc-shaped screen stars 1 of the same material and the same stability. This contributes in particular to an increased fineness of the star screen when the radial gap width W _R is greater than the lateral gap width Ws. Since the fingers 5a expediently do not taper off in the direction of their free ends 7, but are flattened at the free end 7, frontal screen gaps 22 could arise with a correspondingly large radial gap width _WR , through which comparatively large, compact particles fall down through the star screen would. The taper in the longitudinal direction of the fingers 5a counteracts this.

figure 8 shows a portion of a screening device with shafts 20 along which screening stars 1 of a second embodiment are arranged. The sieve stars 1 each have fingers 5b which extend in the longitudinal direction of the fingers 5b, ie in the longitudinal direction L ( figure 1 ), at a varying tilt angle α ( figure 3 ) are inclined in such a way that the fingers 5b are curved outwards on both end faces 12 and 13, forming a convex shape. The fingers 5b are flattened at the free ends 7, as in the first exemplary embodiment. You can average BB ( figure 1 ) correspond to the fingers 5a. Due to the meshing of convex sieve stars 1 of the shafts 20 with likewise convex sieve stars 1 of adjacent shafts 20, lateral sieve gaps 21 with punctiform constrictions Ep are formed.

In a modification, the screening device can alternately have first shafts 20 with screening stars 1 of the first exemplary embodiment and second shafts 20 with screening stars 1 of the second exemplary embodiment. Also in such modifications, in which conically tapered screen stars 1 mesh with convexly tapered screen stars 1, punctiform constrictions result for the lateral screen gaps 21.

figure 9 shows a portion of a screening device with the known from the prior art screening stars 1 with fingers 5b and screening stars 1 with fingers 5c modified again. The screen stars 1 with the fingers 5b are on a shaft 20 axially next to each other arranged, and the screen stars 1 with the fingers 5c are arranged on an adjacent shaft 20 axially side by side. In figure 9 for the sieve stars with the fingers 5c, only one sieve star 1 is shown as representative of the others. In the screening device, the screening stars 1 engage with the fingers 5c like a comb in the screening stars 1 with the fingers 5b of the neighboring shaft. The fingers 5c are in finger longitudinal direction L ( figure 1 ) at a varying tilt angle α ( figure 3 ) tapers in such a way that the sieve stars 1 are curved inwards in the area of the fingers 5c on both end faces, whereby the relevant sieve star 1 in the area of the fingers 5c tapers concavely in the direction of the free end 7 of the respective finger 5c. At the free ends 7, the fingers 5c are flattened as in the first embodiment. You can average BB ( figure 1 ) correspond to the fingers 5a.

Through the interaction of sieve stars 1 with convex fingers 5b with sieve stars 1 with concave fingers 5c, lateral sieve gaps 21 are obtained, which are curved in accordance with the convex-concave course of the end faces 12 and 13. This increases the fineness of the star screen, since long, thin particles of material to be screened pass through the curved screen gaps 21 ( figure 9 ) heavier than straight column 21 ( figure 6 ) can happen.

figure 10 shows examples of modified fingers 5d to 5g, each of which differs in terms of the cross-sectional shape in the circular-cylindrical sections BB concentric to the axis of rotation D. The fingers 5d to 5g are in the direction of the free end of the respective finger, ie in the longitudinal direction of the finger L ( figure 1 ), tapered and can correspond to the fingers 5a or the fingers 5b or the fingers 5c with respect to the taper in the longitudinal direction L in particular and replace the respective type of finger within a screening device.

The finger 5d has the shape of a rectangle in section B-B. It differs from the finger 5a of the first exemplary embodiment only in that the front surface 10 and the rear surface 11 are also straight in the respective section B-B.

The finger 5e corresponds to the finger 5a of the first exemplary embodiment in the area of the front surface 10 and the two end faces 12 and 13, but is convex in the shape of an arrow on the rear surface 11 in contrast thereto.

The finger 5f has two parallel faces 12 and 13, an arrow-shaped convex front surface 10 and an arrow-shaped convex rear surface 11 in section B-B.

The finger 5g has parallel end faces 12 and 13 over about half of its circumferential extent, a rear surface 11 orthogonal thereto and straight in section B-B and a front surface 10 semi-oval, for example circular or elliptical, in section B-B.

In the Figures 11 to 14 a sieve star 1 according to the invention is shown. The screening star 1 differs from the screening star 1 known from the prior art with regard to the shape of the circular-cylindrical cross-section BB concentric to the axis of rotation D and otherwise corresponds to the first exemplary embodiment. The fingers of the sieve star 1 are designated as fingers 5h to distinguish them from the fingers of the exemplary embodiments explained above. In the front view of the figure 11 and the perspective view of figure 14 a cleaning finger, as in the first exemplary embodiment, is not shown. This is due to the fact that the cleaning element 9 ( figure 1 ) is attached only after the forming of the screen star 1 forming plastic body and figure 11 shows the sieve star 1 before the cleaning element 9 is attached.

The fingers 5h taper from the foot area 6 in the direction of the free end 7, i.e. in the longitudinal direction L of the fingers, like the fingers 5a of the first exemplary embodiment. Unlike the fingers 5a, however, the fingers 5h also taper over at least the majority of their circumferential extension measured in the circumferential direction T.

figure 12 shows the in figure 11 registered cut BB. The circumferential direction T coincides with the direction of rotation of the sieve star 1 and is in figure 12 also registered. In the circular-cylindrical cross-section BB, the fingers 5b have the shape of a trapezium, in which the front surface 10 pointing in the direction of rotation forms the long base and the rear surface 11 pointing against the direction of rotation forms the short base. The fingers 5h taper in the circumferential direction T, in the fourth exemplary embodiment counter to the direction of rotation T, on both end faces symmetrically, so that the trapezoidal shape is obtained in section BB. The front surface 10, the rear surface 11 and the two end faces 12 and 13 are each straight in section BB. In the transitions 14 and 15, as already explained for the first exemplary embodiment, they extend over comparatively large radii of curvature into each other. The end faces 12 and 13 each enclose an acute angle 2β in the sections BB, the bisector of which is the central cross-sectional plane Q. The angle of inclination β relative to the radial section plane Q is at least 4° or at least 5°. The angle of inclination β is preferably at most 15° or at most 10°.

In longitudinal sections, such as in figure 13 section AA shown, due to the double taper, firstly in the longitudinal direction L of the fingers and secondly in the circumferential direction T, in the radially inner area of the fingers 5h, such as in the foot area 6, initially there is a taper, while the fingers 5h are in a radially outer expand area. In figure 13 Therefore, in the area of the upper finger 5h shown in section, the outer contour of the trailing finger 5h in the direction of rotation T can be seen and in the area of the lower finger 5h shown in section, the outer contour of the finger 5h leading in the direction of rotation T can be seen.

The superimposition of the taper in the finger longitudinal direction L and the taper in the circumferential direction T is also in the perspective of figure 14 clearly recognizable in each case in the foot area 6.

In alternative embodiments, the sieve star 1 of the fourth exemplary embodiment can also be convex in accordance with the second exemplary embodiment or tapered concavely in accordance with the third exemplary embodiment in relation to the taper in the finger longitudinal direction L.

figure 15 shows examples of further modified fingers 5i to 5m, each of which differs in terms of the cross-sectional shape in the circular-cylindrical sections BB concentric to the axis of rotation D. The fingers 5i to 5m are in the direction of the free end of the respective finger, ie in the longitudinal direction L ( figures 1 and 11 ), tapered and can correspond to the fingers 5a or 5h or instead to the fingers 5b or the fingers 5c in relation to the taper in the longitudinal direction L and can replace the respective type of finger within a screening device. They differ from the fingers 5a and 5d to 5g in that they taper in the circumferential direction T over at least the majority of their circumferential extent, corresponding to the finger 5h.

The finger 5i is derived from the finger 5h of the fourth exemplary embodiment and differs from it in that the front surface 10 and the rear surface 11 are each convexly curved over the entire width of the finger 5d.

The finger 5j is triangular in section B-B, with the "point" of the triangle trailing in the direction of rotation T.

The finger 5k has, in section B-B, an arrow-shaped front surface 10, an axially extending rear surface 11 and two straight end faces 12 and 13 which taper towards one another at an acute angle against the direction of rotation T.

The finger 51 is diamond-shaped in section B-B with two end faces 12 and 13, which run from a circumferentially central, wide area in the direction of rotation T to the front surface 10, which is only designed as a "tip", and also counter to the direction of rotation T to the also only as "Pointed" trained rear surface 11 run. The finger 51 is as a result in both circumferential directions, i. H. in the direction of rotation T and against the direction of rotation T, tapered in the shape of an arrow.

The finger 5m is oval in section B-B, e.g. elliptical, with the extent in the circumferential direction T greater than the axial extent, i. H. larger than the width. The oval shape, for example an elliptical shape, is favorable in view of the wear that occurs during operation and also because of the constriction that forms in the lateral screen gap in a punctiform manner for reducing the adhesion of cohesive screenings components.

In the representations of the fingers 5d to 5g and 5i to 5m, the transitions between the surfaces 10 to 13 are each represented as edges. In preferred embodiments, however, these fingers are also softly rounded at the relevant transitions with a radius of curvature of at least 1.5 mm or, preferably, at least 2 mm.

figure 16 shows meshing star screens 1 of the first exemplary embodiment in a relative rotational position to one another, in which just one finger 5a of one sieve star 1 is in maximum overlap with a finger 5a of the other sieve star 1. Due to the taper at least essentially in the longitudinal direction L of the fingers 5a is formed between the two overlapping fingers 5a a linear constriction E _L . The lateral screen gap existing between the momentarily overlapping fingers 5a widens upwards and downwards, starting from the constriction E _L . This design of the screen gaps counteracts the adhesion of cohesive screened material components and thus the so-called disc formation. This reduces the drive power required to operate the screening device.

the Figures 17 and 18 show two meshing star screen 1 of the fourth embodiment. In figure 17 the cooperating screen stars 1 just take a rotational position in which a finger 5h of a screen star 1 has a slight overlap with one of the fingers 5h of the other screen star 1. Because of the double taper, only a punctiform constriction E _P forms between the overlapping fingers 5h. When the sieve stars 1 continue to rotate, the overlap increases. Two punctiform constrictions form E _P , which, starting from the state of the initial overlap, migrate in the direction of the two free ends of the overlapping fingers 5h. This turning state is in figure 18 shown. If the relevant fingers 5h dip even further into the overlap, the axial width ( figure 6 ) of the lateral screen gap existing between these two fingers 5h. Due to the double taper and the resulting punctiform bottlenecks E _P , the adhesion of cohesive screenings components and thus the formation of discs is counteracted even more effectively.

References:

1

sieve star

2

hub

3

passage

4

Federation

5a-m

finger

6

finger foot area

7

free end

8th

-

9

cleaning element

10

Front, front surface

11

back, back surface

12

Front face, left front face

13

front face, right front face

14

front transition

15

backward transition

16

-

17

-

18

-

19

-

20

Wave

21

lateral sieve gap

22

frontal screen gap

BE

width of the free end

bf

Width in the finger foot area

B.N

width of the hub

D

axis of rotation

DN

diameter of the hub

IE

diameter of the enveloping circle

el

bottleneck

ep

bottleneck

R

radial direction

T

Circumferential direction, direction of rotation

X

axial direction

Ws

lateral gap width

WR

radial gap width

Claims (15)

1. A screening star for a screening device, the screening star comprising:

   1.1 a hub (2) for non-rotatably arranging the screening star (1) on a rotatable shaft (20); and

   1.2 elastically flexible fingers (5a-m) which protrude radially outwards from the hub (2) in a distribution in the circumferential direction about a rotational axis (D) of the screening star (1) and which each extend in the circumferential direction (T) from a base region (6) up to a free end (7) which is a trailing end in the rotational direction,

   1.3 wherein the fingers (5a-m) each comprise a left-hand end-facing area (12) and a right-hand end-facing area (13), and the end-facing areas (12, 13) each exhibit an inclination (α) with respect to a central cross-sectional plane (Q) of the screening star (1), such that the end-facing areas (12, 13) converge in the direction (L) of the free end (7) of the respective finger (5a-m), and the fingers (5a-m) taper in the direction (L) of the free end (7) of the respective finger (5a-m) on both end-facing sides (12, 13) of the screening star (1),

   wherein that
   1.4 the fingers (5a-m) taper, in circular-cylindrical sections (B-B) which are concentric with respect to the rotational axis (D), in a circumferential direction (T) on at least one end-facing area (12, 13).
2. The screening star according to claim 1, wherein the fingers (5a-m) each taper on both end-facing sides (12, 13) over at least most of their length as measured from the base region (6) up to the free end (7).
3. The screening star according to any one of the preceding claims, wherein the fingers (5a-m) taper progressively outwards on both end-facing sides (12, 13) of the screening star (1) in the direction (L) of the free end (7) of the respective finger (5a-m) symmetrically in relation to a cross-sectional plane (Q) of the screening star (1).
4. The screening star according to any one of the preceding claims, wherein the fingers (5a; 5h) conically taper progressively outwards on both end-facing sides (12, 13) of the screening star (1) in the direction (L) of the free end (7) of the respective finger (5a; 5h) at a constant angle of inclination (α), or the fingers (5b) taper progressively outwards on both end-facing sides (12, 13) of the screening star (1) in the direction (L) of the free end (7) of the respective finger (5b) at a varying angle of inclination (α), such that the two end-facing sides (12, 13) are curved convexly outwards or concavely inwards in a round shape.
5. The screening star according to any one of the preceding claims, wherein the fingers (5a-m) taper, in circular-cylindrical sections (B-B) which are concentric with respect to the rotational axis (D), in a circumferential direction (T) on both end-facing areas (12, 13).
6. The screening star according to the preceding claim, wherein the fingers (5a-m) taper in the circumferential direction (T), in the circular-cylindrical sections (B-B), symmetrically with respect to a cross-sectional plane (Q) of the screening star (1).
7. The screening star according to any one of the preceding claims, wherein the fingers (5h; 5i) each at least substantially form, in the circular-cylindrical sections (B-B), an isosceles trapezium comprising a long base which is a leading side in the rotational direction (T) and a short base which is a trailing side in the rotational direction (T).
8. The screening star according to any one of claims 1 to 6, wherein the fingers (5m) are oval in circular-cylindrical sections (B-B) which are concentric with respect to the rotational axis (D).
9. The screening star according to any one of the preceding claims, wherein the fingers (5a; 5e; 5g; 5i; 5m) each comprise, in circular-cylindrical sections (B-B) which are concentric with respect to the rotational axis (D), a front side (10) pointing in the rotational direction (T), a rear side (11) pointing counter to the rotational direction (T), a left-hand end-facing area (12) and a right-hand end-facing area (13), and wherein in circular-cylindrical sections (B-B) which are concentric with respect to the rotational axis (D), the front side (10) is curved outwards in a round shape in the rotational direction (T) at least over most of the axial width of the respective finger (5a; 5e; 5g; 5i; 5m) and/or the rear side (11) is curved outwards in a round shape counter to the rotational direction (T) at least over most of the axial width of the respective finger (5a; 5e; 5g; 5i; 5m).
10. The screening star according to any one of the preceding claims, wherein the hub (2) and the fingers (5a-m) which are tapered on both sides are moulded together in one piece from plastic.
11. The screening star according to any one of the preceding claims, wherein the hub (2) and fingers (5a-m) are each moulded from a plastic material, and the plastic material in a central region of the hub (2) has a higher Shore hardness than the plastic material in the base region (6) of the fingers (5a-m) and/or the plastic material in the region of the free ends (7) of the fingers (5a-m) has a higher Shore hardness than the plastic material in the base region (6) of the fingers (5a-m).
12. A screening device, comprising:

    12.1 multiple shafts (20) arranged next to each other such that they can each rotate about a rotational axis (D); and

    12.2 for each shaft (20), multiple screening stars (1) arranged axially next to each other and non-rotatably connected to the respective shaft (20), each according to any one of the preceding claims,

    12.3 wherein the screening stars (1) of adjacent shafts (20) interlock and mesh, such that the end-facing areas (12, 13) of axially adjacent screening stars (1) delineate lateral screening gaps (21) and the free ends (7) of the screening stars (1) delineate frontal screening gaps (22).
13. The screening device according to the preceding claim, wherein the lateral screening gaps (21) each exhibit a lateral gap width (Ws) orthogonally with respect to the mutually facing end-facing areas (12, 13) of axially adjacent screening stars (1), and the frontal screening gaps (22) each exhibit a radial width gap width (W_R), and the lateral gap width (Ws) is smaller than the radial gap width (W_R).
14. The screening device according to any one of the immediately preceding two claims, wherein the mutually meshing screening stars (1) comprising mutually facing end-facing areas (12, 13) form linear constrictions (E_L) or punctiform constrictions (E_P) in accordance with their tapering, and the lateral gap width (Ws) is measured axially across the constriction (E_L; E_P).
15. The screening device according to any one of the immediately preceding three claims, comprising a drive device for rotary-driving the shafts (20), wherein the drive device is designed to drive adjacent shafts (20) at different rotational speeds.

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