Screening device for plansifters for fractionating ground cereal products

Abstract

According to one aspect of the present invention, a screening device for plansifters is provided. Said screening device has a screen frame (21) for a screen. The screening device forms a top-side and bottom-side stack structure at mutually corresponding positions on the top side and bottom side. The top-side and the bottom-side stack structures are coordinated with one another in the sense that, during the stacking of a plurality of the screening devices, the top screening device is defined in its horizontal position relative to the bottom screening device. The top-side stack structure has a first ramp (61), and the bottom-side stack structure has a second ramp (62), wherein the first ramp (61) and the second ramp (62) fit together so as to transmit force when a bottom and a top screening device are stacked on each other.

Description

[0001] SCREENING DEVICE FOR PLAN SIFTS FOR

[0002] FRACTIONATION OF GRAIN MILLING PRODUCTS

[0003] The invention relates to machines, for example, plansifters, such as those used for fractionating ground grain products. It particularly relates to a screening device for a plansifter.

[0004] Plansifters are used to separate the components of a ground product into coarser and finer grains, and, depending on the specific requirements, also into components of different densities, as well as to remove foreign matter from the ground product. The separation of the ground product into components of different grain sizes is also called "classifying" or "fractionating." Plansifters are generally used in the milling industry to fractionate the ground grain products between and after passes through the roller mill of a grain mill. They can also be used for so-called control sifting, i.e., the sieving of flour that is otherwise ready for sale.

[0005] Plan sifters have screening compartments, each containing a stack of plan screens, which are set into horizontal oscillating movements by a suitable drive mechanism, particularly in circular oscillations in the screening plane. The screens are each mounted on

[0006] Primary frames, so-called "insert frames," are clamped together, which in turn are inserted into sieve frames (also referred to here as "secondary frames"). Between the stacked sieve frames, seals, for example made of suitable felt, are provided at the level of the sieve mesh to prevent the product from escaping undesirably from the sides.

[0007] To ensure that the screen frames are precisely aligned, a closed screen box is generally provided to guide the screen frames. The screen frames can be inserted into or removed from the screen box through a door. However, such a closed screen box has the disadvantage that part of the available space is used for the box walls and its door. Furthermore, the removal and insertion of individual screen frames is only possible in one direction (through the door), and the removal and insertion of screen frames that are not positioned at the top of the screen stack is cumbersome and sometimes not possible at all without removing the screen frames above them.

[0008] Plan sifters with open screen stacks, without a box, have therefore already been proposed. In these, the correct alignment of the screen frames of the screen stack must be ensured by suitable structures, namely grooves on the top, into which ribs arranged on the underside of the screen frame of the screen device above engage; a pin-and-hole connection is also already known. However, such a solution places high demands on the accuracy of fit to prevent undesirable relative movement between the screen frames during the oscillating movements of the plansifter. In addition, to remove and insert a screen device, the screen device to be removed - along with all screen devices above it - must be lifted across its entire depth with a tool, because the groove-and-rib connection otherwise prevents horizontal movement. Contaminants can also accumulate in the groove over time.US 2008 / 0257791 A1 relates to a stackable screen frame for sifters. The screen frame has side walls that form a labyrinth seal when stacked. For this purpose, the side walls have horizontal and inclined surfaces on the top and bottom that match each other. The labyrinth seal is also intended to ensure vertical alignment of the screen frames relative to each other. To achieve the labyrinth seal effect, the angles between the horizontal and inclined surfaces must be comparatively large, namely close to 90°.

[0009] It is an object of the present invention to provide a screening device for plansifters—and a plansifter—that at least partially remedy this problem. In particular, the screening device should enable the formation of open screen stacks without causing the disadvantages described.

[0010] This problem is solved by the invention as defined in the patent claims.

[0011] According to one aspect of the present invention, a screening device for plansifters is provided. This device has a screening frame for a screen. The screening device forms an upper and lower stacking structure at corresponding positions (same xy positions in the coordinate system used here, whose z-axis corresponds to the vertical) on the upper and lower sides. The upper and lower stacking structures are coordinated with one another in the sense that when several of the screening devices are stacked, the upper screening device is defined in its horizontal position relative to the lower screening device. The upper stacking structure has a first ramp, and the lower stacking structure has a second ramp, wherein the first and second ramps abut one another in a force-transmitting manner when a lower and an upper screening device are stacked on top of one another.

[0012] The top and bottom stack structures can be formed by the screen frame. However, it is also possible for the stack structure to include regions of another element of the screening device, for example, the clamping frame described below. In any case, in embodiments, the screen frame forms the bottom stack structure as well as elements of the top stack structure, so that in the stack, screen frames of the stacked screening devices rest on one another and the screen frame extends over the entire height of the screening device. In particular, an outer wall surface of the stack can be formed entirely by outer wall surfaces of the stacked screen frames.

[0013] A ramp in the sense of this text is formed by a surface section which is flat in some areas and is inclined both horizontally and vertically.

[0014] A force-transmitting engagement of the first and the second ramp requires, among other things, that the first and the second ramp run parallel to each other, ie locally, at corresponding positions (xy positions) they have the same angle of inclination (identical normal vectors).

[0015] Because the first and second ramps abut one another in a force-transmitting manner, the upper screening device is not only supported with respect to the lower screening device on which it rests, but is also aligned in its horizontal position, without the need for precisely matched groove-rib structures with the disadvantages discussed above. This also results in an advantage with regard to the sealing effect, particularly in combination with the principle described below of attaching the screening device to an insert frame, which is inserted into a trough-like structure of the screening frame. Therefore, the superimposed ramps are arranged above the screening frame rather than on the screening level.

[0016] It is therefore particularly provided that the insert frame with the sieve is positioned in such a way that the plane of the sieve is arranged below the first ramp and, for example, also above the second ramp, i.e. in a central position with respect to the vertical, in contrast to the prior art, which provides for the sieve at the very top of the sieve frame.

[0017] In particular, it can be provided that the upper screening device rests only on ramps (inclined surfaces) of the lower screening device, and that there is therefore no force-transmitting contact of horizontal surfaces on one another.

[0018] In particular, the first ramp can slope outwards and the second ramp can slope inwards. However, the reverse is also possible, i.e., the first ramp can slope inwards and the second ramp can slope outwards. In particular, it is also possible to combine these two possibilities, i.e., the upper stacking structure can have one ramp sloping outwards and one ramp sloping inwards, with the lower stacking structure correspondingly having one ramp sloping inwards and one ramp sloping outwards, which will be described in more detail below.

[0019] It has been shown that the design of the stacking structures with ramps can solve another problem: The screening device can be removed from a stack by lifting it slightly on one side and then pulling it toward that side (assuming there are no overlying screening devices that rest their full weight on the screening device to be removed). In many designs, this can be done without tools. This is a substantial advantage, because screening stacks are often not equally accessible from all sides, and even lifting them from the inaccessible side (the 'rear') can be quite challenging without tools.

[0020] In this text, stacking and the correspondingly formed stack generally refer to a proper stacking, in which the outer contours of the stacked screening devices are generally aligned with one another, and the upper screening device rests on the lower screening device in a stable manner and, due to the inventive procedure, free of play with respect to horizontal displacement, with the screen generally lying horizontally. The stacked screening devices can, in particular, have substantially the same outer contours, so that the outer wall surfaces of the stacked screening devices are flush with one another.

[0021] It is particularly advantageous if the first ramp and the second ramp have an angle of between 25° and 65° or between 15° and 60°, especially between 30° and 50°, for example, approximately 45° to the horizontal. In this range, the desired effect described above is achieved, while at the same time, removal by lifting from the front and pulling out is easily possible, which is not so easy with steeper ramps (angles greater than 50°, 60°, or 65°).

[0022] In addition to the first and second ramps, the upper stacking structure can also have a third ramp on the upper side, and the lower stacking structure can have a corresponding fourth ramp on the lower side, with the slopes of the third and fourth ramps also corresponding to each other (they can correspond to the slope of the first and second ramps, but this is not necessary). If the first ramp slopes outwards and the second ramp slopes inwards, the third ramp slopes inwards and the fourth ramp slopes outwards.

[0023] If the first and third ramps, as well as the second and fourth ramps, each belong to the same wall section, the centering effect of the ramps also acts locally, pairing a wall section of the upper screening device with a wall section of the lower screening device. This ensures that the stack structure is very stable even when the walls are only thin and therefore still slightly flexible.

[0024] The first and second ramps are, in particular, designed to extend circumferentially around the screening device, i.e., they extend, for example, continuously along the entire circumference of the screening frame or at least along a substantial portion thereof. The third and fourth ramps can also be circumferential, if desired.

[0025] The screening device can be multi-walled. Depending on the configuration, one or two rows of (vertical) passage channels can be present. Passage channels are generally vertical channels located on the side of the screen frame through which screenings can fall downwards into a lower screen frame or an outlet line. From the passage channels, the screenings falling through these either reach a screen of the (correspondingly differently configured) screening device below, or into a passage channel of the screening device below, or possibly into an outlet line. In this case, in addition to an outer wall surface (which, for example, merges into the first or second ramp at the top or bottom) and an inner wall surface (possibly with the third and fourth ramp), there are also sections of wall surfaces surrounding the passage channels.A vertical section through the passageways therefore results in several wall sections. In this case, for example, at least the outermost wall section - which also forms the outer wall surface - will have the stack structures of the type described. However, it is also possible for wall sections further inward, in addition to the outermost wall section, and for example for all wall sections to each have an upper and a lower stack structure of the type described. Coordinated ramps can, in particular, run circumferentially around the passageways, i.e. a passageway wall around the passageway has a bevel on the upper side and a projection forming a ramp on the lower side.Therefore, it is also possible, for example, for the third ramp of the outermost wall section to run along the contour of a passage channel and thus merge continuously into the first ramp of the next inner wall section; analogously for the fourth ramp of the outermost wall section and the second ramp of the next inner wall section, etc.

[0026] In some embodiments, the screening device has, in addition to the screening frame, an insert frame to which the screening is fastened. The screening frame can in particular have a circumferential side wall and an inwardly projecting support on which the insert frame rests, in such a way that the screening lies within the circumferential side wall - i.e. the circumferential side wall surrounds the insert frame with the screening on the outside, along an outer boundary (edge ​​or similar) of the insert frame. In addition, the screening can lie below an upper edge of the circumferential side wall, so that the screening frame essentially forms a trough in which the insert frame with the screening lies, for example with a precise fit, i.e. immobile in the horizontal direction relative to the screening frame.This has the advantage, among other things, that the upper stack structure is not arranged at the level of the screen, which is why no screen presses against the seal formed by the adjacent ramps under hydrostatic pressure (if the screened material is considered a fluid for this case). Rather, only ground material dust comes into contact with the ramps. It turns out that due to this measure, as well as the slope of the ramps, the sealing effect is already sufficient, without the stack structures requiring additional sealants.

[0027] The insert frame can be metallic – for example, it can be designed as a flat metallic body (thin plate) with at least one large-area recess spanned by the screen. The insert frame can, for example, have an outer frame section that is essentially rectangular overall, with dimensions adapted to the support. In addition to the outer frame section, a system of at least one bar, spanned by the screen, for example, with a rectangular cross-section, can also be present. The screen can optionally also be metallic. It can be designed as a flat body, in particular as a metal sheet, with the screen openings as through holes. The screen can be welded to the insert frame.

[0028] In addition to the screen frame and the insert frame, some embodiments of the screen device also include a clamping frame. The clamping frame is arranged so that the insert frame is fixed between the support and the clamping frame. The clamping frame can fit precisely into the recess formed within an upper section (above the support) of the surrounding side wall of the screen frame.

[0029] In embodiments, the clamping frame can be shaped so that its inner surface is flush with the inner surface of the lower section (below the clamping frame) of the surrounding side wall. Additionally or alternatively, the clamping frame can be flush with the upper edge of the surrounding side wall, i.e., its height can correspond to the height of the upper section of the surrounding side wall, minus the thickness of the insert frame.

[0030] The clamping frame can, for example, have the shape of a rectangular profile.

[0031] The clamping frame can also be made of metal, possibly with a thermally insulating filling material.

[0032] If necessary, the clamping frame can form the third ramp or a region (part) thereof by having a bevel on the top-inside.

[0033] In addition to the screening device, the present invention also relates to a plansifter comprising at least one stack of screening devices of the type described here, in addition to a drive mechanism which sets this stack in horizontally oscillating movements, for example circular movements.

[0034] Embodiments of the invention are described below with reference to the drawings. In the drawings, like reference numerals denote like or similar elements. The drawings show partially corresponding elements in different sizes from figure to figure. They show:

[0035] Fig. 1 : a view of a plansifter with closed sieve compartments;

[0036] Fig. 2: a plansifter with open sieve stacks;

[0037] Fig. 3: an exploded view of a screening device with screen, primary frame, clamping frame, and insert frame; Fig. 4: a view of two partially sectioned, stacked screening devices;

[0038] Fig. 5 shows the screening devices of Fig. 4 in plan, elevation and side view; and

[0039] Fig. 6 is an enlarged detail of Fig. 5.

[0040] Figure 1 shows a plansifter 1 as used in grain mills. The plansifter comprises a plurality of screening compartments mounted in a space via a common suspension device 4 so that common horizontal oscillating movements are possible. A drive (not visible in Fig. 1) is configured to set the ensemble of screening compartments into, for example, horizontal circular oscillations. In addition, the plansifter has flexible feed lines 6 as the screening material inlet and likewise flexible outlet lines 7 as the screening material outlet. Each screening compartment has a stack of screening devices arranged one above the other. In the embodiment of Fig. 1, the screening compartments are provided in screening boxes 3, each of which forms a housing for the screening compartments. In such embodiments, the screening devices arranged one above the other in a stack can be guided by corresponding structures of the housing.

[0041] As an alternative to the sieve compartments provided in sieve box 3, sieve compartments can also be formed by open sieve stacks, in which a housing surrounding the sieve stacks is omitted.

[0042] Figure 2 shows an embodiment of such a plansifter with open sieve stacks in a particularly space-saving arrangement, although some elements (suspension device, feed lines, some outlet lines) are not shown. A frame 11 serves as the mechanical support structure. It forms a supporting frame for the upper sieve stacks 12 and the lower sieve stacks 13 and, in the illustrated embodiment, also accommodates drive modules not visible in the figure. The sieve stacks are attached directly or indirectly to the frame 11, for example, by means of a clamping system consisting of rods and / or belts and / or other means; the clamping system is not shown in Fig. 2.

[0043] Drive modules for a modular structure, which can be accommodated in a frame 11 of the type shown in Fig. 2, are described in Swiss patent application 000722 / 2022. However, the present invention is independent of the design of the plansifter drive and also works for plansifters with a central drive device, as is often found, and as is present centrally between the screen boxes 3 in a plansifter of the type shown in Fig. 1.

[0044] The upper sieve stacks 12 and lower sieve stacks 13 in Fig. 2 are each formed from a plurality of sieve devices 20 of the type described below, wherein the sieve devices are stacked directly on top of one another, and wherein a closing element 14 and 15, respectively, is present on the top side of the upper sieve stack 12 and on the bottom side of the lower sieve stack, through which the material to be sieved is fed in or removed. The sieves can have different mesh sizes, and the configuration of the sieve stacks can be selected by the user as required. A plansifter with closed sieve compartments as shown in Fig. 1 can also have sieve devices 20 according to the description below.

[0045] Figure 3 shows an exploded view of a screening device 20. Figure 4 shows a view of two partially sectioned, stacked screening devices 20. Figure 5 shows a top view of the screening devices 20 of Figure 4, as well as sections through planes AA and BB in the top view, i.e., Figure 5 shows a plan view, elevation view, and side view of the arrangement of Figure 4. Figure 6 shows detail D from section AA in Figure 5.

[0046] A sieve frame 21 forms a mechanical support structure of the sieve device 20. An insert frame 22 (primary frame) supports the sieve 23. For example, as shown in the Swiss patent application 000837 / 2022, the sieve 23 can be designed as a metallic foil with perforations as sieve holes, wherein the foil is welded onto the - also metallic - insert frame 22.

[0047] In addition to the sieve frame 21 and the insert frame 22 with the sieve 23 attached thereto, the sieve device also has a clamping frame 24 which holds the - flat - insert frame 22 and the sieve 23 relative to the sieve frame 21.

[0048] The sieve frame has a circumferential side wall 30 and, towards the sides, two rows or one row or no rows of at least one passage channel 31 each, so that the side wall forms wall sections on the very outside, the very inside, and optionally between the passage channels 31. In the illustrated embodiment, two rows each with two passage channels 31 are present on two opposite sides (top and bottom in the plan view according to Fig. 5), while the other two opposite sides each have one row with two passage channels 31. The arrangement of passage channels can vary from sieving device to sieving device in order to guide fractions of the sieved material fed in through the feed lines and separated by the sieves as intended.

[0049] Below the sieve 23, a collection area is formed for each screening device, which is closed off at the bottom by a collecting base 33 of the sieve frame 21. The collection area is open on at least one side in order to discharge fine particles of the screening material that have passed through the sieve (the so-called through-fall) through a laterally arranged slotted opening 37 that opens into a passage channel 31. On the other sides, the collection area is closed off by a lower section 38 of the circumferential side wall 30 formed by the sieve frame. The other passage channels 31 of the upper screening device shown in the figures serve as drop channels, i.e. for passing screening material that comes from a screening device or a screening material inlet located higher up to lower down.

[0050] The sieve 23 has lateral sieve passage openings 41 on the sieve level through which parts of the sieve material that have not been sieved through the sieve (the so-called rejects) can fall through.

[0051] The sieve frame 21 forms a circumferential support for the insert frame 22. Where the collecting area is closed off at the sides by the lower section 38 of the circumferential side wall 30, the support can be formed by a shoulder 34, while elsewhere, above the lateral slot opening 37, it is formed by an inwardly projecting projection 35. The support is uninterrupted along the circumferential line of the insert frame 22.

[0052] In embodiments, the sieve frame is at least partially metallic. In such embodiments, the collecting base can be formed by a base plate and the surrounding side wall can be constructed in several parts, with several wall elements, for example with an outer wall element which forms the outer wall surface, a lower inner wall element which forms the inner wall surface of the lower section 38, an upper inner wall element which forms the inner wall surface of the upper section 39, and several passage channel wall elements which surround the passage channels. A thermally insulating filling material can be arranged in the spaces between the wall elements. The shoulder 34 and the projection 35, i.e. the support, can be formed by an intermediate base.

[0053] The dimensions of the screen frame 21 on the one hand and the clamping frame 24 on the other hand are coordinated so that the clamping frame fits exactly into the receptacle that is created within the upper part of the surrounding side wall.

[0054] In addition, the height of the clamping frame 24 is adapted to the distance between the support and the upper edge 40 of the surrounding side wall as well as to the thickness of the insert frame 22, so that the upper edge of the clamping frame 24 is at the same height as the upper edge 40 of the surrounding side wall, so that the clamping frame 24 acts like a part of the sieve frame 21 when the sieve devices 20 are stacked and can be perceived.

[0055] In particular, in Figure 6, it can be seen that the screening devices 20 have an upper stacking structure and a lower stacking structure at corresponding horizontal positions (xy positions), see the Cartesian coordinate system indicated in the upper and right panels of Figure 5. When the screening devices are stacked on top of each other as intended, the lower stacking structure of the upper screening device rests on the upper stacking structure of the lower screening device.

[0056] The upper stacking structure includes an outwardly sloping first ramp 61, upon which rests an inwardly sloping second ramp 62 of the lower stacking structure of the upper screening device 20. In the illustrated embodiment, the outwardly sloping first ramp 61 and the inwardly sloping second ramp 62 are flat and parallel to each other. They form an angle of between 25° and 65°, in particular between 30° and 50°, to the horizontal.

[0057] “Inside” and “outside” are to be understood in relation to the screening device as a whole, ie “inside” is the side of a wall facing the screen and the collection area, while “outside” is the opposite side, on the left in Figure 6.

[0058] The upper and lower stack structures are designed such that the first and second ramps 61, 62 rest on each other in a force-transmitting manner. Therefore, there is generally no force-transmitting contact with the upper edge 40 – the surface of the screen frame runs horizontally and flat there, or is curved in alternative embodiments. Rather, a distance a exists between the upper edge 40 and the counter surface 50 on the underside. Depending on manufacturing tolerances, the distance a may be very small, amounting to 1-2 mm or even less.

[0059] In the illustrated embodiment, the upper-side stack structure, in addition to the outwardly sloping first ramp 61, also has an upper-side, inwardly sloping third ramp 63, and correspondingly, the lower-side stack structure has a lower, outwardly sloping fourth ramp 64. Therefore, the centering effect of the ramps also acts locally, for each pairing of a wall section of the upper screening device with a wall section of the lower screening device. This ensures that the stack structure is very stable even when the walls are only slightly thick and are therefore still slightly flexible. Due to the passage channels 31, the screening frames 21 have several wall sections depending on the configuration in the vertical section (sections AA and BB in Fig. 5 and Fig. 6).In the illustrated embodiment, for example, there are two wall sections on each of the two sides, and three wall sections on the other two sides, corresponding to the two rows of passageways. With multiple wall sections per side, the illustrated stacked structure is present at least on the outermost wall, and for example, on every wall. In the illustrated embodiment, each wall has a stacked structure of the type described, which can also be seen in Fig. 5 in sections AA and BB, as well as in Fig. 6.

[0060] In the innermost wall section, the inwardly sloping third ramp 63 is not formed by the screen frame, but by the clamping frame 24, which is shown on the right in Fig. 6.

[0061] The inwardly sloping second ramp 62 of the lower stack structure and, if applicable, its outwardly sloping fourth ramp 64 are each formed in the illustrated embodiment by a downwardly projecting outer or inner rib 51 or 52 of the sieve frame 21, so that the walls of the sieve frame 21 are concave on the underside. Accordingly, the walls of the sieve frame are convex on the top. This has the advantage that residues cannot accumulate in a groove (or other concave upper structure) over time. However, a reverse configuration is not excluded - also due to the very good sealing properties of the sieve frames. This means that it is also possible for the outwardly sloping first ramp of the upper stack structure to be formed by an upwardly projecting rib and, conversely, for the walls of the sieve frame to be convex on the underside.

Claims

PATENT CLAIMS 1. A screening device for a plansifter, comprising a screening frame (21) for supporting a screen (23), the screening device having an upper and lower stacking structure at corresponding positions on the upper side and lower side, respectively, characterized in that the upper stacking structure has a first ramp (61) and the lower stacking structure has a second ramp (62), which are shaped and arranged such that when the screening device as a lower screening device and an identical screening device as an upper screening device are stacked on top of one another, the first ramp (61) of the lower screening device and the second ramp (62) of the upper screening device abut one another in a force-transmitting manner.

2. Screening device according to claim 1, wherein the upper stacking structure and the lower stacking structure are formed such that when the screen as the lower screen and an identical screen as the upper screen are stacked on top of each other, the upper screen rests only on ramps of the lower screen and that there is no force-transmitting contact of horizontal surfaces with each other.

3. Screening device according to claim 1 or 2, wherein the first ramp (61) and the second ramp (62) each have an identical angle of between 30° and 50° to the horizontal.

4. Screening device according to one of the preceding claims, comprising an insert frame (22) to which the screen (23) is fastened, wherein the screen frame (21) forms a circumferential side wall and has an inwardly projecting support on which the insert frame (22) rests.

5. Screening device according to claim 4, wherein the screening device further comprises a clamping frame (24) which is arranged above the insert frame (22) and within an upper part (39) of the circumferential side wall (30) 6. Screening device according to one of the preceding claims, wherein the first ramp (61) slopes outwards and the second ramp (62) slopes inwards.

7. Screening device according to claim 6, wherein the upper-side stacking structure further comprises an upper-side, inwardly sloping third ramp (63) and the lower-side stacking structure further comprises a lower-side, outwardly sloping fourth ramp (64), which are shaped and arranged such that when the screening device as a lower screening device and an identical screening device as an upper screening device are stacked on top of one another, the third ramp (63) of the lower screening device and the fourth ramp (64) of the upper screening device abut one another in a force-transmitting manner.

8. Screening device according to claim 7, wherein wall sections of the screen frame are concave on the underside by forming a downwardly projecting outer rib (51) and a downwardly projecting inner rib (52), wherein the second ramp (62) is formed by the outer rib (51) and the fourth ramp (64) is formed by the inner rib (52).

9. Screening device according to claim 7 or 8, comprising the clamping frame (24), wherein the clamping frame (24) forms at least part of the third ramp (63) by having an inner bevel towards its upper edge.

10. Screening device according to one of claims 7-9, wherein the screen frame (21) forms at least one vertical passage channel (31), wherein a passage channel wall around the passage channel has a bevel on the upper side and a projection forming a ramp on the lower side, so that along a contour of the passage channel a region of the first ramp (61) continuously merges into a region of the third ramp (63) and a region of the second ramp (62) continuously merges into a region of the fourth ramp (64).

11. Plan sifter for fractionating grain mill products for a grain mill, comprising at least one stack with a plurality of screening devices according to one of the preceding claims and a screening material inlet (6) and a screening material outlet (7), wherein the plan sifter is further configured to set the stack in oscillating movements in order to promote the at least partial passage of screening material introduced through the screening material inlet through the screens (23) of the screening devices.

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