EP3209434B1 - Sieve cleaner, sieve unit and method - Google Patents

Description

The invention relates to a sieve cleaner for cleaning a sieve surface of a sieve box which contains the sieve surface and a sieve bottom. In particular, such a sieve cleaner can be designed to clean a sieve surface of a sieve box of a plan sifter. The invention also relates to a sieve unit and a method for upgrading or converting a sieve box.

Movable sieve cleaners which can be placed on a sieve bottom of a sieve box and with the help of which a sieve surface of the sieve box can be cleaned are known per se. Such sieves are stackable and can be arranged, for example, as a sieve stack in plan sifters in order to separate or sift granular to floury products into different fractions and qualities. The sieve cleaners absorb the oscillating movements of the plansifter and the sieve boxes and thereby randomly move around on the sieve base, repeatedly bouncing back against the sieve frame.

• DE 36 40 569 A1 , DE 24 11 455 A1 , DE 29 52 215 A1 ,
• DE 79 36 430 U1 , DE 90 15 461 U1 , DE 86 31 814 U1 ,
• EP 0 536 803 B1 , EP 2 465 616 A1 , WO 99/28053 A1 ,
• DE 1 507 747 A1 , DE 873 345 C , US 2,086,199 und DE 164924 offenbart. Ein bürstenloser Siebreiniger bzw. eine Siebeinheit mit mindestens einem bürstenlosen Siebreiniger gemäß dem Oberbegriff des Anspruchs 1 bzw. 11 ist aus der DE 298 02 807 U1 bekannt.

Screen cleaners are for example from the EP 0 694 341 B1 known. These sieve cleaners contain a wobble foot which extends along a center of gravity of the sieve cleaner and is designed in such a way that it can be placed on the sieve bottom and the sieve cleaner can be tilted around the wobble foot. The movement is influenced by the inertia, the sliding friction between the wobble foot and the sieve bottom and the asymmetrical structure of the sieve cleaner. The actual cleaning effect is achieved by rounded knobs or brushes, which hit the screen surface and / or slide along it due to the wobbling movement of the screen cleaner. Brushes are used more for finer screen areas with mesh sizes in the range of, for example, 85 to 250 μm, and knobs for coarser screen areas with mesh sizes of, for example 250 µm or more. Similar screen cleaners, where cleaning is carried out by knobs or brushes hitting the screen surface, are also popular DE 10 2006 005 970 A1 , U.S. 6,095,339 A ,

• DE 36 40 569 A1 , DE 24 11 455 A1 , DE 29 52 215 A1 ,
• DE 79 36 430 U1 , DE 90 15 461 U1 , DE 86 31 814 U1 ,
• EP 0 536 803 B1 , EP 2 465 616 A1 , WO 99/28053 A1 ,
• DE 1 507 747 A1 , DE 873 345 C , U.S. 2,086,199 and DE 164924 disclosed. A brushless screen cleaner or a screen unit with at least one brushless screen cleaner according to the preamble of claim 1 or 11 is from the DE 298 02 807 U1 known.

However, there are certain disadvantages inherent in all of these known screen cleaners. Because the bristles of the brushes can fail over time due to the mechanical stresses, which is not justifiable from a hygienic point of view - especially if the screen cleaners are used in plansifters in which food such as grain or ground grain products are sifted. It has been shown that screen cleaners with knobs tend to smear the product layer adhering to the screen surface even further instead of loosening it. Furthermore, many of the known sieve cleaners have not proven to be particularly efficient, since they only clean the sieve surface to an inadequate extent. More compact screen cleaners are also in U.S. 1,925,447 and

WO 2010/045284 A1 disclosed. These screen cleaners are composed of simple geometric figures such as spheres, cylinders and polyhedra. Tests with at least similar screen cleaners have shown, however, that these tend to clog the screen surface.

In view of the disadvantages of the prior art, it is an object of the present invention to provide an improved and / or alternative screen cleaner. In particular, the screen cleaner should clean the screen surface as efficiently as possible without damaging it or the screen frame, while also complying with the hygiene requirements the processing of food should be complied with.

In a complex and extensive series of tests, a large number of the most varied forms of possible screen cleaners were tested with regard to the fulfillment of the above requirements. For example, screen cleaners with silicone rags or aluminum pins were used instead of knobs or brushes, eccentric centers of gravity were created, the elastic properties were varied, influences of the dimensions and their proportions were evaluated, etc. Screen cleaner proved to be particularly beneficial.

The stated objects are thus achieved in a first aspect of the invention by a screen cleaner according to claim 1. This screen cleaner
is designed for cleaning a sieve surface of a sieve box which contains the sieve surface and a sieve bottom. The screen surface can be a screen mesh, for example. The screen cleaner can be designed, for example, to clean a screen surface, such as a screen mesh, a screen box of a plan sifter. The sieve cleaner contains a wobble foot which extends along a main axis of the sieve cleaner and is designed in such a way that it can be placed on the sieve bottom and the sieve cleaner can be tilted around this wobble foot. The named main axis can be, for example, a gravity axis of the screen cleaner. Furthermore, the screen cleaner contains at least one cleaning element with a cleaning area, the or each cleaning area having a plurality of cleaning surfaces for cleaning the screen surface.

According to the invention, the cleaning surfaces are each designed for at least linear contact with the screen surface and are separated from one another by slots formed in the cleaning area.

A line-shaped contact is understood here and in the following to be a one-dimensional contact - in contrast to a point-shaped, i.e. zero-dimensional contact that exists between a rounded knob or bristle end known from the prior art and a flat screen surface. The phrase “at least linearly” also includes two-dimensional, that is, two-dimensional, contacts.

The at least linear contact leads to the fact that the cleaning surfaces sweep over a flat, that is two-dimensional area of the sieve surface when they rotate about the main axis of the sieve cleaner. In this way, a significant part of the cleaning is achieved by wiping off the fine material from the sieve surface, which has passed through it. Knocking, as is mainly caused by the knobs known from the prior art, can therefore be neglected. This also reduces the damage to the screen surface associated with knocking off. The slots formed between the cleaning surfaces ensure that the fine material can partially pass through these slots. This prevents the fine material from being merely brushed into the sieve surface by the cleaning areas or the sieve surface from being pushed away by the sieve cleaner due to the accumulating fine material. Overall, the screen cleaners according to the invention therefore have the advantage that they can clean the screen surface at least as well or even more efficiently than those from the prior art were able to do. This advantage also exists for sieve surfaces, in particular sieve fabrics, with smaller mesh sizes, for which sieve cleaners with brushes were used in the prior art, in particular for sieve surfaces with mesh sizes of less than 250 μm, preferably less than 180 μm, more preferably less than 150 μm , even more preferably less than 125 µm and particularly preferably less than 90 µm.

The wobble foot can be rounded, which simplifies tilting and increases the freedom of movement of the screen cleaner. The cleaning area does not contain brushes. As no bristles can tear out, the screen cleaner can meet hygiene requirements.

According to the invention, the slots extend in a slot direction which, with a radial direction with respect to the main axis, enclose an angle which is in the range from 30 ° to 60 ° and particularly preferably from 40 ° to 50 ° and very particularly preferably 45 °. Such angles provide more wiping edges, which are particularly useful in different directions of movement.

When rotating about the main axis, the cleaning surfaces each sweep over an imaginary cleaning line in a radial direction with respect to the main axis. The ratio of the radial distance between two adjacent cleaning lines and the radial length of the cleaning lines is preferably in the range of 50% and 100%, particularly preferably 90% and 95%.

Alternatively, it is also conceivable and within the scope of the invention that the cleaning lines of the individual cleaning surfaces adjoin one another directly or even overlap one another. The cleaning elements, in particular the preferred cleaning arms explained below, can have a height parallel to the main axis, and the slots can have a depth parallel to the main axis. The ratio between the depth of the slots and the height of the cleaning elements, in particular the cleaning arms, is preferably greater than 0% and less than or equal to 20%; the ratio is preferably about 10%. The greater this ratio, the lower the sliding friction between the screen cleaner and the screen surface and the setting of the fine material and at a given height of the cleaning elements the less there is the risk of the screen cleaner coming to a standstill. On the other hand, ratios that are too large would lead to the fine material getting stuck in the slots to a high degree.

The slots of one and the same cleaning element advantageously run parallel to one another.

The screen cleaner particularly advantageously has a central area containing the main axis with an upper side opposite the wobble foot, which is recessed in relation to the cleaning surfaces in such a way that it cannot be brought into contact with the screen surface, in particular not in contact with an essentially flat screen surface is. In particular, the above-mentioned upper side does not form a cleaning surface for cleaning the sieve surface. This is because cleaning surfaces that are present on the upper side of the central area and are not recessed with respect to the cleaning surfaces of the cleaning elements would lead to these coming into contact with the screen surface even when the screen cleaner was not tilted. This would slow down or even jam the sieve cleaner between the sieve bottom and the sieve surface.

The screen cleaner preferably contains at least three cleaning elements, in particular at least three cleaning arms as described in detail below. In this embodiment, each of the at least three cleaning elements is provided with a respective cleaning area, each cleaning area having a plurality of cleaning surfaces for cleaning the sieve surface. The cleaning surfaces are arranged and designed in such a way that when the sieve box is at a standstill (i.e. especially in the absence of the movements of the sieve box that support the sieving) and when the sieve surface is taut, the cleaning surfaces of at least two of the cleaning elements, but not the cleaning surfaces of all of the cleaning elements, are in contact at the same time with the sieve surface are or can be brought are, whereby essentially all cleaning surfaces of these cleaning elements are or can be brought into contact with the screen surface.

In other words, it is not possible to bring all cleaning elements into contact with the sieve surface at the same time. Instead, due to the tumbling motion of the screen cleaner, the cleaning surfaces of other cleaning elements keep coming into contact with the screen surface. The slots of the cleaning elements that are not in contact with the sieve surface can be emptied. For example, if the screen cleaner contains exactly three cleaning elements, then when the screen box is at a standstill and when the screen surface is taut, exactly two cleaning elements are in contact with the screen surface at the same time.

If the cleaning surfaces of two or more cleaning elements are in contact with the sieve surface at the same time, then essentially all of the cleaning surfaces of these cleaning elements are in contact with the sieve surface. "Essentially all" means that at least 50%, preferably at least 70%, more preferably at least 90% and particularly preferably all cleaning surfaces of the two cleaning elements mentioned are in contact with the sieve surface. In this embodiment it is therefore excluded, for example, that of two cleaning elements only a single cleaning surface is in contact with the sieve surface. In this way, the contact with the sieve surface and thus also the cleaning effect are increased.

The screen cleaner is advantageously made of a sufficiently elastic material. For this purpose, it has proven to be advantageous to manufacture the screen cleaner from a relatively soft polyurethane, such as from a Elastollan ^®, which is available from BASF. Elastollan ^® is also permitted for the processing of food, such as Grain or flour products. Elastic materials have the advantage, among other things, that a sieve frame of the sieve box is less damaged when the sieve cleaner hits it. The screen cleaners according to the invention can be produced, for example, in an injection molding process.

The screen cleaner also advantageously has an odd number of cleaning elements, in particular cleaning arms. The number mentioned is preferably at least three and particularly preferably exactly three. The cleaning elements are also preferably distributed uniformly in the circumferential direction. This structure is particularly simple and enables an advantageous compromise between the cleaning effect and the free space formed between the cleaning elements, in particular the cleaning arms.

It is also particularly advantageous that the cleaning element (s) is / are designed as cleaning arm (s) which extend radially outward from a central region of the screen cleaner containing the main axis. This also contributes to the mentioned advantageous compromise.

It is also preferred if the cleaning surfaces are arranged in a row along the cleaning arms. This also achieves a sufficiently low sliding friction between the screen cleaner and the screen surface, which prevents the slots from being clogged by the fine material and also prevents the screen cleaner from coming to a standstill.

The cleaning arms can have a length which is in the range from 5 to 15 cm, preferably 6.5 to 7.5 cm. The cleaning areas also preferably have a radial length, the ratio of this radial length to the length of the cleaning arms being in the range from 50 to 100% and preferably about 85%.

Impact protectors can be arranged at the outer ends of the cleaning elements, in particular the cleaning arms. This can reduce the risk that the cleaning surfaces will wear out due to contact with the sieve frame. The impact guards can be designed, for example, as reinforcements of the cleaning elements in a plane running perpendicular to the main axis.

In order to remove the fine material removed from the sieve surface with the aid of the cleaning elements from the sieve box, the sieve cleaner can have at least one scraper for clearing out fine material located on the sieve bottom through a clearing opening formed in a sieve frame of the sieve box. Such a clearing opening is advantageously arranged at the end of a cleaning arm.

The screen cleaner is preferably designed in one piece. This makes it easier to manufacture and further reduces the risk of individual components being lost.

Another aspect of the invention relates to a sieve unit according to claim 10.

This contains at least one sieve box with a sieve bottom and a sieve surface, in particular a sieve fabric, as well as at least one sieve cleaner that can be or is placed on the sieve bottom.

The screen cleaner of the screen unit according to the invention has at least three cleaning elements, in particular three cleaning arms, with a respective cleaning area, each cleaning area having a plurality of cleaning surfaces for cleaning the screen surface. The cleaning surfaces are arranged and designed in such a way that when the sieve box is at a standstill (i.e. in particular in the absence of the movements of the sieve box that support the sieving) and when the sieve surface is taut, the cleaning surfaces of at least two of the cleaning elements, but not the cleaning surfaces of all cleaning elements are or can be brought into contact with the sieve surface at the same time, in which case essentially all cleaning surfaces of these cleaning elements are or can be brought into contact with the sieve surface.

This and other advantages can be achieved in that the sieve cleaner has at least three cleaning elements and the sieve cleaner and the sieve box are designed and coordinated in such a way that when the sieve box is at a standstill (i.e. in particular in the absence of the movements of the sieve box that support the sieving), with correctly clamped sieve surface and when the wobble foot rests on the sieve bottom, the cleaning surfaces of all cleaning elements are at a distance of less than 5 mm, preferably less than 3 mm, particularly preferably less than 1.4 mm from the sieve surface. Because of this small maximum distance from the sieve surface, the speed component that is perpendicular to the sieve surface, i.e. in particular vertical, is limited with which the cleaning surfaces hit the sieve surface when the sieve cleaner tilts around the wobble foot.

As already explained above, efficient cleaning of the screen surface is also possible if the mesh size of the screen surface, in particular of the screen fabric, is less than 250 μm, preferably less than 180 μm, more preferably less than 150 μm, even more preferably less than 125 µm and particularly preferably smaller than 90 µm.

Finally, another aspect of the invention relates to a method for upgrading or converting a sieve box according to claim 12. In this method, a sieve cleaner according to the invention is placed on a sieve bottom of the sieve box in such a way that a sieve unit as described above is formed.

Figur 1:

einen ersten nicht erfindungsgemässen Siebreiniger in einer perspektivischen Ansicht;

Figur 2:

einen zweiten nicht erfindungsgemässen Siebreiniger in einer perspektivischen Ansicht;

Figur 3:

einen dritten erfindungsgemässen Siebreiniger in einer perspektivischen Ansicht;

Figur 4:

eine Skizze zur Veranschaulichung der von den Reinigungsflächen der Siebreiniger gemäss Figuren 2 und 3 überstrichenen Reinigungslinien;

Figur 5:

einen vierten erfindungsgemässen Siebreiniger in einer perspektivischen Ansicht;

Figur 6:

den vierten erfindungsgemässen Siebreiniger in einer ersten Seitenansicht;

Figur 7:

den vierten erfindungsgemässen Siebreiniger in einer zweiten Ansicht;

Figur 8:

den vierten erfindungsgemässen Siebreiniger in einer Draufsicht;

Figur 9:

eine Schnittansicht des vierten erfindungsgemässen Siebreinigers entlang der Linie A-A gemäss Figur 8;

Figur 10:

eine Seitenansicht des in einem Siebkasten aufgenommenen vierten erfindungsgemässen Siebreinigers.

The invention is explained in more detail below using several exemplary embodiments and drawings. Show it

Figure 1:

a first screen cleaner not according to the invention in a perspective view;

Figure 2:

a second screen cleaner not according to the invention in a perspective view;

Figure 3:

a third screen cleaner according to the invention in a perspective view;

Figure 4:

a sketch to illustrate the cleaning surfaces of the screen cleaner according to Figures 2 and 3 swept cleaning lines;

Figure 5:

a fourth screen cleaner according to the invention in a perspective view;

Figure 6:

the fourth screen cleaner according to the invention in a first side view;

Figure 7:

the fourth screen cleaner according to the invention in a second view;

Figure 8:

the fourth screen cleaner according to the invention in a plan view;

Figure 9:

a sectional view of the fourth screen cleaner according to the invention along the line AA according to FIG Figure 8 ;

Figure 10:

a side view of the fourth screen cleaner according to the invention accommodated in a screen box.

In the Figure 1 The illustrated first embodiment of the screen cleaner 1 ', not according to the invention, contains a wobble foot, which cannot be seen here. This extends along a main axis A 'of the screen cleaner 1', which at the same time also forms one of its axes of gravity. He is trained like the wobble foot 5 in the fourth exemplary embodiment according to the invention Figures 5 to 9 .

From a central region 10 'of the screen cleaner 1', three cleaning elements, designed as cleaning arms 6 ', extend which are distributed uniformly in the circumferential direction around the center of gravity A'. Each of the cleaning arms 6 'contains a respective cleaning area 7'. Each of the cleaning areas 7 'has a large number of rectangular cleaning surfaces 8' which run perpendicular to the center of gravity A 'and are each designed for flat contact with a screen surface (not shown here) (see FIG Figure 10 which shows a sieve box and a sieve cleaner according to the invention arranged therein). The cleaning surfaces 8 'are separated from one another by the slots 9' formed in the respective cleaning area 7 '. In the first exemplary embodiment shown here, the slots 9 'extend along a slot direction S' which, with a direction R 'which is radial with respect to the center of gravity axis A', enclose an angle α 'which is 90 °. In other words, the slots 9 'extend transversely to the longitudinal direction of the cleaning arms 6'.

Cleaning areas 18 'are also present in the area between two of the cleaning arms 6', that is to say in the central area 10 'of the screen cleaner 1'. In addition, the middle area 10 'contains three openings 19' through which fine material can pass. When the sieve box is at a standstill and the sieve surface is taut, the cleaning surfaces 8 'of exactly two of the cleaning arms 6' can always be brought into contact with a sieve surface at the same time, with essentially all of the cleaning surfaces 8 'of these two cleaning arms 6' being able to be brought into contact with the sieve surface.

The second screen cleaner 1 "according to the invention, not according to the invention Figure 2 differs from the one in Figure 1 shown by the fact that in In the middle area 10 "neither cleaning areas 18 'nor openings 19' are present. Due to the absence of cleaning areas 18 'in the middle area 10", contact between the screen cleaner 1 "and the screen surface occurs only when the screen cleaner 1" is tilted. This can prevent the sieve cleaner 1 ″ from being braked or even jammed between the sieve bottom and the sieve surface before it can even tip over.

Figure 3 shows a third screen cleaner 1 according to the invention, which also contains three cleaning arms 6 ‴ evenly distributed in the circumferential direction. The screen cleaner 1 ‴ also has a wobble foot 5 ‴, which is rounded at the lower end, which makes it easier to tilt the screen cleaner 1 ‴.

In contrast to the ones in the Figures 1 and 2 In the illustrated embodiments, the slots 9 formed between the cleaning surfaces 8 ‴ run in a slot direction S ‴ which enclose an angle α ‴ of 45 ° with a radial direction R ‴ with respect to the center of gravity A ‴. This angle creates a particularly advantageous compromise between the line support and the sliding friction between the screen cleaner 1 ‴ and the screen surface. Furthermore, reinforcements 11 ‴ are provided at the ends of the cleaning arms 6 in a plane perpendicular to the main axis A ‴, which act as impact protectors and reduce the risk of damage to the cleaning areas when the screen cleaner 1 ‴ hits a screen frame. This is done using Figure 4 explained in more detail. This shows on the left a plan view of a section of a cleaning arm 6 ″ of the not according to the invention

Sieve cleaner 1 "according to Figure 2 and on the right a top view of a section of a cleaning arm 6 ‴ of the screen cleaner 1 ‴ according to Figure 3 . When moving in the circumferential direction U, the cleaning surfaces 8 ″ and 8 ‴ each sweep an imaginary cleaning line L ″ or L ‴. Due to the inclination of the cleaning surfaces 8 ‴ and the slots 9 ‴ for the third embodiment shown on the right, the ratio of the radial length of the cleaning lines L ″ and the distance between two adjacent cleaning lines L ″ is greater than This is the case with the second exemplary embodiment shown on the left. The line contact is thus greater in the third exemplary embodiment than in the second. For this reason, the third screen cleaner 1 effects more efficient cleaning than the first screen cleaner 1 ″ not according to the invention.

In the Figures 5 to 9 a preferred screen cleaner 1 is shown in a fourth embodiment. This sieve cleaner 1 can for instance be manufactured integrally by an injection molding process from the above-mentioned Elastollan ^®. This screen cleaner 1 also has a wobble foot 5 which extends along a center of gravity axis A, which forms a main axis of the screen cleaner 1. The wobble foot 5 is designed in such a way that it can be placed on a sieve bottom and the sieve cleaner 1 can be tilted around the wobble foot 5. The wobble foot 5 is also rounded at the lower end, as a result of which the tilting of the sieve cleaner 1 is simplified. Here, too, the three cleaning arms 6 are evenly distributed around the center of gravity A in the circumferential direction. In this embodiment too, reinforcements 11 are provided at the ends of the cleaning arms 6 in a plane perpendicular to the main axis A, which act as impact protectors and reduce the risk of damage to the cleaning areas when the screen cleaner 1 hits a screen frame.

In contrast to the screen cleaner 1 ‴ according to Figure 3 the top 15 of the central region 10 is recessed in relation to the cleaning surfaces 8 of the cleaning arms 6 in such a way that this top 15 cannot be brought into contact with a sieve surface.

This results in the same advantages as those already mentioned above in connection with the one not according to the invention

Figure 2 have been explained. Furthermore, the screen cleaner 1 contains a clearer 12, with the aid of which fine material located on a sieve bottom can be cleared out through a clearing opening formed in a sieve frame of the sieve box. Figure 6 shows a first side view of the fourth screen cleaner 1, Figure 7 a second side view and Figure 8 a top view.

Figure 9 shows a detailed sectional view along the line AA according to FIG Figure 8 . It can be seen that the cleaning surfaces 8 are rounded. However, since they run in a straight line perpendicular to this sectional view, linear contact with a flat screen surface is still possible.

According to Figure 9 the slots 9 have a depth t = 1.5 mm parallel to the center of gravity A, which cannot be seen here. The ratio between this depth t and the height h of the cleaning arms 6 is approximately 10%.

In Figure 10 Finally, a sieve unit is shown which contains a sieve box 3 and one of the preferred sieve cleaners 1 according to the invention. The sieve box 3 has a horizontal sieve bottom 4, a sieve frame 13 extending therefrom in the vertical direction and a sieve surface designed as a sieve fabric 2, which is stretched over the sieve frame 13. The sieve cleaner 1 is placed on the sieve bottom 4 with its wobble foot 5. When the screen box 3 is at a standstill and the screen fabric 2 is taut, the cleaning surfaces of exactly two of the cleaning arms 6 are always in contact with the screen fabric 2 at the same time Screen cleaner 1 designed in such a way that the cleaning surfaces 8 of all cleaning arms 6 are always at a distance of less than 1.4 mm from the screen fabric 2.

Claims (12)

1. A brushless sieve cleaner (1; 1'; 1"; 1‴) for cleaning a sieving surface (2) of a sieve box (3) comprising the sieving surface (2) and a sieve floor (4), comprising

   - a wobble foot (5; 5") extending along a main axis (A; A'; A") of the brushless sieve cleaner (1; 1'; 1''; 1‴) and configured such that the wobble foot be placed on the sieve floor (4) and the brushless sieve cleaner (1; 1'; 1"; 1‴) can be tilted about the wobble foot (5; 5");

   - at least one cleaning element (6; 6'; 6"; 6‴) comprising a brushless cleaning region (7; 7'; 7"; 7‴) containing no brushes, the or each cleaning region (7; 7'; 7"; 7‴) comprising a plurality of cleaning surfaces (8; 8'; 8"; 8‴) for cleaning the sieving surface (2); characterized in that
   each one of said plurality of cleaning surfaces (8; 8'; 8"; 8‴) is respectively adapted for at least linear contact with said sieving surface (2), wherein upon rotation of said brushless sieve cleaner (1; 1'; 1"; 1‴) about the main axis (A; A'; A"; A‴), each individual one of the plurality of cleaning surfaces (8; 8'; 8"; 8‴) sweeps over a planar region of the sieving surface (2), and in that each individual one of the plurality of cleaning surfaces (8; 8'; 8"; 8‴) is separated from each adjacent cleaning surface (8; 8'; 8"; 8‴) by a slot (9; 9'; 9"; 9‴) formed in the cleaning area (7; 7'; 7"; 7‴), and that each slot (9; 9‴) extends in a slot direction (S; S‴) which is at an angle (α‴) in the range of 30° to 60° to a radial direction (R; R‴) with respect to the main axis (A; A‴).
2. Brushless sieve cleaner (1; 1'; 1"; 1‴) according to claim 1, characterized in that
   each of the planar region of the sieving surface (2) swept over by the cleaning surfaces (8; 8'; 8"; 8‴) defines a notional cleaning line (L"; L‴), which coincides with a radial dimension of the planar region of the sieving surface (2) in a radial direction (R; R'; R"; R‴) with respect to the main axis (A; A'; A"; A‴), and wherein a radial distance between two adjacent cleaning lines (L"; L‴) is either shorter than the radial length of the cleaning lines (L"; L‴) or is not present.
3. Brushless sieve cleaner (1; 1'; 1"; 1‴) according to any one of the preceding claims, characterized in that the cleaning elements (6; 6'; 6"; 6‴) have a height (h) parallel to the main axis (A; A'; A"; A‴) and the slots (9; 9'; 9"; 9‴) have a depth (t) parallel to the main axis (A), the depth (t) of the slots (9; 9'; 9"; 9‴) being greater than 0% and less than or equal to 20% of the height (h) of the cleaning elements (6; 6'; 6"; 6‴).
4. Brushless sieve cleaner (1; 1'') according to any one of the preceding claims, characterized in that it has a central region (10; 10'') containing the main axis (A; A'; A") and having an upper side (15; 15'') opposite the wobble foot (5, 5''), which upper side is recessed with respect to the cleaning surfaces (8; 8'') in such a way that it cannot be brought into contact with the sieveing surface (2).
5. A brushless sieve cleaner (1; 1'; 1"; 1‴) according to any one of the preceding claims, characterized by at least three cleaning elements (6; 6'; 6"; 6‴) having a respective cleaning region (7; 7'; 7"; 7‴), each cleaning region (7; 7'; 7"; 7‴) having a plurality of cleaning surfaces (8; 8'; 8"; 8‴) for cleaning the sieving surface (2), and the cleaning surfaces (8; 8'; 8"; 8") are arranged and formed in such a way that, when the brushless sieve cleaner (1; 1'; 1"; 1‴) is placed on the sieve floor (4) and when the sieve box (3) is at a standstill and the sieving surface (2) is taut, at least 50% of the cleaning surfaces (8; 8'; 8"; 8‴) of at least two of the cleaning elements (6; 6'; 6"; 6‴), but not the cleaning surfaces (8; 8'; 8"; 8‴) of all the cleaning elements (6; 6'; 6"; 6‴), are simultaneously in contact with the sieving surface (2).
6. Brushless sieve cleaner (1; 1'; 1"; 1‴) according to any one of the preceding claims, characterized in that the brushless sieve cleaner (1; 1'; 1"; 1‴) has an odd number of cleaning elements (6; 6'; 6"; 6‴).
7. Brushless sieve cleaner (1; 1'; 1"; 1‴) according to any one of the preceding claims, characterized in that the cleaning element(s) (6; 6'; 6"; 6‴) is/are designed as cleaning arm(s) (6; 6'; 6"; 6‴) which extends radially outwards from a central region (10; 10'; 10"; 10‴) of the brushless sieve cleaner (1; 1'; 1"; 1‴) containing the main axis (A; A'; A"; A‴).
8. Brushless sieve cleaner (1; 1"; 1‴) according to claim 7, characterized in that
   the cleaning surfaces (8; 8"; 8‴) are arranged in a single row along the cleaning arms (6; 6"; 6‴).
9. A brushless sieve cleaner (1; 1'; 1"; 1‴) according to any one of claims 7 and 8, characterized in that the cleaning arms (6; 6'; 6"; 6‴) have a length (l ₁, l ₂) that is in the range of 5 to 15 cm.
10. Sieve unit, comprising

    - at least one sieve box (3) with a sieve floor (4) and a sieving surface (2);

    - at least one brushless sieve cleaner (1; 1'; 1''; 1‴) which is placed on the sieve floor (4),

    characterized in that

    the brushless sieve cleaner (1; 1'; 1"; 1‴) has a wobble foot (5; 5‴) which extends along a main axis (A; A'; A"; A‴) of the brushless sieve cleaner (1; 1'; 1"; 1‴) and is designed in such a way that it can be placed on the sieve floor (4) and the brushless sieve cleaner (1; 1'; 1"; 1‴) can be tilted about the wobble foot (5; 5‴),

    and that the brushless sieve cleaner (1; 1'; 1"; 1‴) comprises at least three cleaning elements (6; 6'; 6''; 6‴) with a respective cleaning region (7; 7'; 7"; 7‴), each cleaning region (7; 7'; 7"; 7‴) comprising a plurality of cleaning surfaces (8; 8'; 8"; 8‴) for cleaning the sieving surface (2), and

    in that the cleaning surfaces (8; 8'; 8"; 8‴) are arranged and formed in such a way that, when the brushless sieve cleaner (1; 1'; 1"; 1‴) is placed on the sieve floor (4), when the sieve box (3) is at a standstill and when the sieving surface (2) is taut, at least 50% of the cleaning surfaces (8; 8'; 8"; 8‴) of at least two of the cleaning elements (6; 6'; 6"; 6‴), but not the cleaning surfaces (8; 8'; 8"; 8‴) of all the cleaning elements (6; 6'; 6"; 6‴), are simultaneously in contact with the sieving surface (2), and in that each individual one of the plurality of cleaning surfaces is separated from each adjacent cleaning surface by slots formed in the cleaning region, and in that the cleaning surfaces (8; 8'; 8"; 8‴) of the cleaning elements (6; 6'; 6"; 6‴) are separated from each adjacent cleaning surface by slots formed in the cleaning region, and

    in that each slot (9; 9") extends in a slot direction (S; S") which is at an angle (α") in the range from 30° to 60° to a radial direction (R; R") with respect to the main axis (A; A").
11. Sieve unit according to claim 10,
    characterized in that the brushless sieve cleaner (1; 1'; 1"; 1‴) and the sieve box (3) are designed in such a way that, when the sieve box (3) is at a standstill, when the sieving surface (2) is taut and when the wobble foot (5; 5‴) rests on the sieve floor (4), each of the cleaning surfaces (8; 8'; 8"; 8‴) of all cleaning elements (6; 6'; 6"; 6‴) is at a distance of less than 5 mm from the sieving surface (2).
12. A method of upgrading or retrofitting a sieve box (3), comprising a step of placing a brushless sieve cleaner (1) according to any one of claims 1 to 9 on a sieve floor (4) of the sieve box (3) so as to form a sieve unit according to any one of claims 10 and 11.

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