DE29623207U1 - Device for dosing bulk goods or pasty masses - Google Patents

Description

Description

Device for dosing bulk materials or pasty masses

The invention relates to a device for dosing bulk materials or pasty masses according to the preamble of claim 1. Accordingly, it contains a movable part with one or more recesses, the thickness of this movable part being greater than the largest grain size of the material being conveyed and this thickness, the number and size of the recesses as well as the speed of the movable part influencing the discharge speed (= dosing) of the material being conveyed. Such dosing devices are known.

The closest state of the art that we know of are dosing devices such as those used in plants for the production of ready-mixed mortar - apart from the water, of course. Each additive, in particular sand, cement and lime, is stored in its own silo, which has a dosing device at the bottom.

Figures 1 to 3 show a section of such a system, each of the lower area of a sand silo 20 with a downwardly tapering funnel 21, which opens downwards into a dosing device 22. This dosing device 22 contains a substantially cylindrical roller 23 with a horizontally arranged axis of rotation. This roller 23 contains two axially extending recesses 24. Apart from a small amount of play required for mobility and to compensate for thermal expansion, the inner diameter of the housing in the middle area of the dosing device 22 corresponds to the outer diameter of the roller 23.

Fig. 1 shows this dosing device 22 with a roller position such that one of the two recesses 24 opens upwards, i.e. towards the funnel 21, so that from here - driven by gravity - sand 2 enters the recess 24.

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Fig. 2 shows the same device 22 in the next phase, where the roller 23 has rotated clockwise so much that the recess 24 in question is no longer open at the top and is not yet open at the bottom. The casing side of the recess 24 is closed by the adjacent part of the housing.

Fig. 3 finally shows the same device 22 in the next phase, where the roller 23 has rotated clockwise far enough that the recess 24 in question is open downwards, so that the sand escapes from it 24 - again driven by gravity - downwards to a vibrating mixer or the like.

If the roller 23 is shut down, either because it is time to finish work or because of a malfunction (for example, due to a failure of the downstream mixer or conveyor belt), no more sand is conveyed because the recesses 24 of the roller 23 are never open both upwards and downwards at the same time. However, this advantageous property is paid for by frequent jamming. The recurring malfunctions caused by such jamming are extremely annoying because the entire system can come to a standstill, the dosing ratios are not precisely maintained during the stop and subsequent restart phases, and the jamming can only be eliminated by a complex removal of the roller and cleaning it as well as cleaning the housing part that interacts with the roller. The biggest problem is that the silo must be emptied before the roller can be removed.

This tendency to jam has ruled out the use of such dosing devices in the emptying of settling tanks in wastewater treatment plants, where maximum reliability is required.

The inventors therefore set themselves the task of specifying a similarly simple dosing device that seals perfectly when not in use, but does not lead to jamming and also requires extremely little maintenance. This dosing device should also be particularly suitable for the interval-controlled discharge of sand from the bottom of a settling tank in a wastewater treatment plant.

The inventors first studied the previously known dosing device and recognized that the rotating roller pushes fine components of the sand into the sealing gap between the roller and the housing.

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Sand never consists of grains of the same size, but there are finer and coarser crystals. Therefore, there can be no sealing gap dimensioning that prevents any grain of sand from penetrating the sealing gap. The inventors then realized that this tendency for sand to form can be reduced if the sealing gap (26) is allowed to expand continuously along the main conveying direction (H). However, in a position in the middle, between those shown in Figures 1 and 2, the seal is no longer perfect when stationary, so that the other part of the problem is not solved.

The problem is solved by the preamble of claim 1 through its characterizing features, according to which the dosing device

a) contains three parts arranged in succession in the conveying direction, of which the first part, referred to as the upstream orifice, and the third part, referred to as the downstream orifice, can be moved perpendicularly to the "main conveying direction" and/or the middle part, referred to below as the "movable part" (even if it is immobile in a variant), whereby

b) the pre-diaphragm has one or more recesses referred to as "pre-holes" in such an arrangement that during a movement cycle of the movable part relative to the diaphragms, at least one pre-hole and one recess of the movable part at least partially overlap in a phase range I and do not overlap at all in another phase range II+III+IV, and that

c) the after-diaphragm has one or more recesses referred to as "after-holes" in such an arrangement that during a movement cycle of the movable part relative to the diaphragms 5 and 8, at least one after-hole and one recess of the movable part at least partially overlap in a phase region III and do not overlap at all in another phase region IV+I+II, whereby

d) phase areas I and III do not overlap at any time, so that at any time it is impossible for any recess of the movable part to be open to both a pre-hole and a post-hole.

The essence of the invention is to change the relative movement between the movable part and the apertures, whereby these three parts interact in a similar way to the roller and housing of the previously known dosing device, so that it is no longer essentially tangential but orthogonal to the main conveying direction.

RENTEC dosing device

In most applications it is sensible to leave the main conveying direction approximately vertical in order to be able to use gravity as a reliable means of propulsion. The direction of movement of the moving part should therefore preferably be approximately horizontal. With this change in the direction of movement, gravity continues to fill the material to be conveyed into the recesses of the moving part in a phase area I and also to empty it from there in a later phase area III. In the preferred embodiment according to claim 5, in which the moving part - similar to the roller in the previously known device continuously rotates or is rotated when the material to be conveyed is discharged - in contrast to the previously known device, the filling and emptying of the material to be conveyed into and from the recesses now takes place not via the shell side, but via the front side of the cylindrical moving part, which is preferred for this design. The axis of rotation of the moving part is approximately vertical in this design.

The change in the direction of movement according to the invention with respect to the main conveying pressure, usually with respect to gravity, excludes in a surprisingly simple manner all cladding induced by self-locking between the movable part and the housing part interacting with it. According to claim 2, the direction of movement of the movable part should deviate by at least degrees from the main conveying direction or the vertical, more preferably according to claim 3 by at least 80 degrees.

Although the rotation of the moving part preferred according to claim 5 leads to the most effective and reliable design according to previous experience, a periodic back and forth movement according to claim 4 is also possible. It is only necessary that the movement cycle for each recess in the moving part provides non-overlapping phases I and III of filling or emptying of conveyed material.

The movement of the movable part is preferably carried out in one plane for the sake of greatest possible simplicity, however, this is not mandatory: For a back and forth movement, the movable part can also be designed as a section of a cylinder surface and can be pivoted back and forth by an angle of no more than +/- 40 degrees around an approximately horizontal axis.

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The preferred rotational movement does not have to take place on a cylindrical surface - although this has the advantage of being as simple as possible - but can also be carried out on a conical surface, for example. For this purpose, the movable part is then not essentially cylindrical but frustoconical. In such a design, the end faces are preferably conical rather than flat, and preferably with such a tip angle dimension and orientation that both the top and bottom of the surface and end face meet perpendicularly at their respective circular boundary edges.

3With a small tip angle ß between the rotation axis and the cone surface, approximately up to 20 degrees, the angle @ between the rotation axis and the vertical can match the angle ß and preferably oriented in such a way that filling takes place via an inclined front side (up to approximately 40 degrees), but emptying takes place via a horizontal front side; the emptying resistance is thus smaller than the filling resistance, which makes it more difficult for material to be conveyed to adhere to the moving part.

The cone tip angle ß can also grow significantly beyond 20 degrees, but @ should not grow with it, and may even be reduced to 0 again. At ß = 90 degrees, the layering of truncated cones degenerates into a concentric nesting of rings; such a design is also quite interesting for some applications, especially those where strong centrifugal forces are to be used as a propulsion medium.

Devices according to the invention with a conical or annular design of the apertures and/or the movable part are the subject of claims 6 to 9 and are described in more detail later with reference to Figures 9 and II.

The extremely effective change in the direction of movement compared to the known state of the art no longer allows sealing transversely to the direction of movement by means of a simple front cover on both sides; rather, according to feature b of claim 1, a front cover with openings referred to as "pre-holes" is required for filling the material to be conveyed into the recesses of the moving part.

To further combat blockages, claim 10 teaches that each pre-hole is smaller than each recess in the movable part and each post-hole is larger than each recess. Further preferably, according to claim 12, the pre-hole, recess and post-hole should be of similar shape. Particularly preferably, according to claim 11, the inequalities mentioned in claim 10 should not only refer to the respective end face size but also to the largest and smallest dimensions of the same.

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These developments according to claims 10 to 12, preferably in combination with one another, ensure that every particle that can penetrate a pre-hole can also be picked up by a recess and emptied from it again via a post-hole, and thus also allow the dosing of materials that are otherwise extremely difficult to dose, such as highly inhomogeneous sand and gravel and - also sticky sludge from these. They are therefore particularly recommended according to claim 19 for use in the dosed discharge of materials from basins of sewage treatment plants or sludge processing plants and the like.

In order to make the dosing device as simple as possible, the front and rear orifices are preferably rigidly connected to the housing, preferably screwed in. However, it is also possible for the front and/or rear orifices to move. According to claim 13, small oscillating movements are suitable for the orifices in order to reduce friction and adhesion of the conveyed material to the ends. The amplitude of these oscillations must be so small that overlaps between phases I and III are excluded.

Larger movements, even endless ones in the case of rotation, can be permitted for the ends if the two diaphragms are moved synchronously, i.e. with a phase offset u that is constant over time, in accordance with claim 14. This condition is sufficient for the desired function, provided that the phase offset is at least so large that a recess (4) cannot cover a preliminary hole (7) and a subsequent hole (9) at the same time.

Although the gearing effort is greater due to the drive of the diaphragms, the initiation of movement can at least dampen the hardening tendencies that occur in some conveyed materials, e.g. in the case of cement, the gradual setting due to air humidity, to the extent that blockage is hardly possible. For this reason, the front diaphragm in particular is preferably kept in permanent motion. If this permanent motion is only a small oscillating motion, the moving part and the rear diaphragm do not have to move; if the front diaphragm rotates continuously, however, the rear diaphragm must be moved synchronously with a suitable phase offset, as already explained in the explanation of claim 14. The closed position of the dosing device can be achieved with such permanent motion of both diaphragms by the synchronous motion of the moving part arranged between the diaphragms.

RENTEC dosing device

According to claim 16, the opening position is to be achieved with - preferably permanent movement of the apertures in the case of hardening materials being conveyed - by a deviation of the speed of the moving part from that of the apertures; the speed of movement of the moving part can be above or below that of the apertures, it can also be zero according to claim 15 and it can be achieved according to claim 17 by a different movement orientation of the movement of the moving part compared to that of the apertures; the two vector speeds only have to differ from one another in some way, with the size of this difference determining the size of the metered flow rate.

Of the countless possible speed combinations, the stopping of the moving part mentioned in claim 15 - whether only for the delivery of the conveyed goods with permanently running shutters or whether permanently with only the delivery of the conveyed goods with shutters running - is particularly advantageous because this can be achieved by a simple switchable brake opposite the housing.

The combination of equal speed values highlighted in claim 17 is useful at high rotational speeds of the apertures and the moving part located between them to reduce centrifugal forces acting on the conveyed material.

According to claim IS, the material pairing metal/metal should be avoided in the face pairing between the front plate and the moving part and between the moving part and the rear plate. At least one partner of each of the two sliding pairs should be plastic. Peroxide-crosslinked polyester reinforced with microfibers has proven to be particularly effective as a plastic.

The invention is explained in more detail below with reference to Figures 4 to 11. It shows:

Fig. 4 the lower part of a bulk material silo with a dosing device according to the invention with a vertically arranged axis of rotation or axis of rotational symmetry in a schematic cross section,

Fig. 5 shows a scaled plan view of a front panel with three sector-like holes for a device according to Figure 4,

Fig. 6 in a plan view of the same scale a movable part with three sector-like recesses for the same device,

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Fig. 7 in a plan view of the same scale a follow-up aperture with three sector-like follow-up holes for the same device,

Fig. 8 in a top view of the same scale in a view from below a different design of the holes or recesses of the diaphragms and the movable part, each with three spiral-like openings in a matching phase arrangement - chosen here only for easier illustration,

Fig. 9 shows a schematic cross-section of the lower part of a bulk material silo with a conical dosing device according to the invention with a rotation axis or rotational symmetry axis arranged obliquely to the vertical,

Fig. 10 shows a perspective view of a metering device according to the invention with a substantially radial main conveying direction within it, whereby the upper part of the housing and the front panel are removed to make the movable part and the rear panel visible and

Fig. 11 in cross-section to the same scale of the aforementioned dosing device together with the upper part of the housing and the pre-orifice deflecting the main conveying direction.

Fig. 12 shows a schematic cross-section of a sand washing plant with a dosing device according to the invention

Figure 4 shows a schematic cross-section of the lower part of a bulk material silo 20 with a funnel 21 and a metering device 1 according to the invention underneath with a vertically arranged axis of rotation 13 or axis of rotational symmetry. The material to be conveyed 2 moves downwards, following gravity, into the pre-holes 7 of the front orifice plate 5 until it is filled. The front orifice plate 5 is fixed against rotation relative to the housing 6 by means of clamping screws 17. The same applies to the rear orifice plate 8.

In the embodiment shown, three pre-holes 7 are arranged in the front panel and evenly distributed over the circumference, which is why only one appears in the cutting plane. Three and four are the particularly preferred numbers for the pre-holes 7, the recesses 4 in the movable part 3 and the post-holes 9 in the post-panel 8; however, smaller numbers down to 10 are also possible, as are larger numbers up to about eight.

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The number of holes 7, 9 or recesses 4 can be the same in the three interacting parts 5, 8 and 3. The holes or recesses can be evenly distributed over the circumference of the respective component, but do not need to be; it is only important that during a phase called "I" at least one recess 4 in the movable part 3 receives conveyed material 2 from a pre-hole 7 and during a phase called "III" releases conveyed material 2 again through at least one post-hole 9, whereby for each recess 4 it must be ensured by the positioning and dimensioning of the openings 4, 7 and 9 that phases I and III do not overlap. The movable part 3 is arranged below the pre-diaphragm 5 and the post-diaphragm 8 is arranged below it. These three parts 5, 3 and 8 are essentially cylindrical. The movable part 3 is preferably - as shown here - thicker than the pre-panel 5 arranged above it and the post-panel 8 arranged below it. This allows the movable part 3 to receive a significant amount of the conveyed material 2 from above in each of its recesses 4 as soon as the movable part 3 is rotated so far that a recess 4 is located in at least partial overlap below a pre-hole 7 of the panel 5. This phase is called I.

If the movable part 3 is rotated further by a motor 14, the overlap between recess 4 and pre-hole 7 initially becomes even greater and reaches a maximum, preferably lasting a short period of time, which is preferably identical to the cross-sectional area of the pre-hole 7. At maximum overlap, the inflow speed of the conveyed material 2 into the recess 4 is at its greatest, provided that the recess 4 is not already full. If the movable part 3 is rotated further, the overlap between recess 4 and pre-hole 7 decreases again, finally reaching Q and thus the phase of conveyed material filling into the recess 4, designated as I, ends.

A further rotation of the movable part 3 transports the material to be conveyed 2 held in the recess 4 on a circular path sector around the rotation axis 13. In the meantime, the recess 4 is closed at the top by the front baffle 5, at the bottom by the rear baffle 8 and at the side by the housing β, so that no further material to be conveyed 2 penetrates into the recess 4 from above, but also nothing escapes anywhere. This phase is referred to as II in the following.

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In order to enable a high dosing capacity with a small size, phase II should be significantly shorter than phase I, but still long enough that, when all manufacturing, wear and delivery tolerances are exhausted, this phase can be safely adjusted in the angular position of the motor 14 if necessary in order to be able to reliably represent zero material flow.

When the moving part 3 is rotated further (by hand or, as preferred, by means of a motor 14), a recess 4 initially overlaps small, then increasing and finally decreasing again above a secondary hole 9 of the secondary aperture 8. This phase is called III. In III, the moving part 3 can release the quantity of the conveyed material 2 temporarily stored in its recess 4 - downwards - through a secondary hole 9. This phase is shown in Figure 4.

In order to ensure the complete emptying of each recess 4, each associated post-hole 9 should preferably completely cover the recess over a small twist angle range.

A further rotation of the movable part 3 transports the now empty recess 4 on a circular path around the rotation axis 13. In the meantime, the recess 4 is closed at the top by the cover 5, at the bottom by the cover 8 and at the side by the housing 6, so that no further material 2 to be conveyed penetrates into the recess 4 from above. This phase is referred to below as IV.

In order to enable a high dosing capacity with a small size, phase IV should be significantly shorter than phases I and III, but still long enough that, when all manufacturing, wear and feed tolerances in the angular position of the motor 14 are exhausted, this phase can be safely set if necessary in order to be able to reliably represent the conveyed material flow 0. - It is also possible to set only one of the two functionally similar phases II and IV so wide that even feed errors of the motor are still absorbed; however, the control program then becomes more complex.

Of the two long phases I and III, phase III, which is used for emptying, is preferably designed to be slightly longer than filling phase I, because the pressure gradient that can be used for emptying is generally smaller than that for filling. In the case of sticky materials, it is also possible to support the emptying by introducing vibrations.

RENTEC dosing device

The invention basically assumes that the passage of each cycle of phases I to IV involves an unsteady discharge of the conveyed material over time. It is therefore not possible to set a completely uniform trickle, as is the case with one of the previously known throttles. However, the inventors have recognized that such a high degree of continuity in the discharge and collection of the conveyed material is not necessary for most applications, in particular for removing sand from clarification tanks or in the production of ready-mixed mortar; what is more important is a very high level of operational reliability, even under adverse and highly fluctuating operating conditions, combined with high dosing precision.

To reduce the discontinuity of the conveyance, the recesses 4 can be very large; in extreme cases, the sector boundaries between the various recesses can be reduced to metal sheets. To prevent uncontrolled flow, both the upstream and downstream orifices then have only one hole, preferably opposite each other. Both the upstream and downstream holes can be a 120-degree sector, as can almost all three recesses 4 in the moving part 3. The approximate continuity is achieved by the fact that very shortly after the leading recess has just left the filling phase I, the filling phase begins for the next recess, and the same applies on the discharge side.

In addition to improved temporal continuity, spatially distributed conveyance can also be achieved if - while accepting smaller sector divisions - larger opening numbers are used, preferably with a larger number of openings on the moving part than on the apertures.

Figures 5 to 7 show, on the same scale, a matching set consisting of the pre-diaphragm 5 (Figure 5), the movable part 3 (Figure 6) and the post-diaphragm 8 (Figure 7), each in a top view. This set of these three parts is intended for a device according to Figure 4; it is not optimized for continuity, as shown in the two previous paragraphs, but for the greatest possible simplicity and yet good dosing accuracy.

The pre-diaphragm 5 according to Figure 5 has three sector-like pre-holes 7. These pre-holes 7 are evenly distributed over the circumference and each have a sector angle of 30 degrees. The radially inner boundary is given by a circular arc of radius R3 and the outer boundary by a circular arc of radius R4. One of the post-holes 9 of the post-diaphragm 8, which is to be arranged as the part after but one below, is shown in a dashed line to illustrate the phase offset μ.

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The movable part 3 according to Figure 6 has three sector-like recesses 4. These recesses 4 are evenly distributed over the circumference and each have a sector angle of 35 degrees. The radially inner boundary is given by a circular arc of radius R2 and the outer boundary by a circular arc of radius R5.

The after-aperture 8 according to Figure 7 has three sector-like after-holes 9. These after-holes 9 are evenly distributed over the circumference and each have a sector angle of 40 degrees. The radially inner boundary is given by a circular arc of radius Rl and the outer boundary by a circular arc of radius Ro.

The sequence of figures 5 to 7 shows an increase in the sector angles in the flow direction, so that even when choosing the radii according to R1=R2=R3=R4=R5=R6, the cross-sectional areas of the respective opening increase towards the rear, which is already good protection against blockages. This protection is even better with the preferred choice of radius RKR2<R3<R4<R5<R6 shown here. In this way, the inequalities w7<w4<w9 and W7<W4<W9 are also fulfilled.

To reliably prevent direct flow from the upstream orifice to the downstream orifice in any position of the movable part 3 and with η (here: 3) identical openings 7, 4, 9 evenly distributed over the circumference, the following inequality must be fulfilled:

Sector angle of a pre-hole 7 +■ sector angle of a recess 4 + sector angle of a post-hole 9 < 350 degrees divided by n. For the present example, this inequality is:

30 degrees + 35 degrees + 40 degrees < 12C degrees

105 degrees < 120 degrees

In the selected design, there is a safety margin of 5 degrees at each boundary; these small angles, which serve to ensure tolerance insensitivity, determine the length of phases II and IV.

Figure 8 shows a top view of the same scale and a view from below of a different design of the holes or recesses of the diaphragms and the movable part, each with three spiral-like openings in a matching phase arrangement - chosen here only for the sake of ease of illustration; of course, during operation, the pre- and post-diaphragms must be rotated relative to one another so that their respective openings do not overlap.

This embodiment also implements the preferred feature that the pre-hole 7 is the smallest and the post-hole 9 is the largest, while the recess 4 is of medium size.

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The spirals should be oriented so that the radially inner curve areas lead; the orientation shown is therefore best suited to the anti-clockwise direction of rotation of the moving part. With rapid rotation, the centrifugal force supports the emptying along the spirally curved sector boundaries. However, the rotation speed must not be too high - especially with sticky materials being conveyed - because otherwise the centrifugal forces in the material being conveyed, which build up unchanged on the inside of the cylinder surfaces of all three parts, in particular the moving part 3, can lead to sticking to these inner surfaces. Therefore, when conveying sewage sludge at speeds above 40 l/min, a design of the three parts 5, 3 and 8 in plan view according to Figure 8 is preferably combined with a conical design in cross section according to Figure 9:

Figure 9 shows in a schematic cross-section the lower part of a bulk material silo 20 with funnel 21 and with a conical dosing device according to the invention with ■ rotation axis 13 or rotational symmetry axis arranged at an angle @ to the vertical V. According to this embodiment, the movable part 3 not only has a conical outer surface 10, but - as preferred its upper end surface II and the lower end surface 12 are also conical.

Preferably - as shown here - the angle @ is equal to the cone angle ß between the rotation axis 13 and the shell surface 10, so that on one side - preferably on the emptying side, as shown here - the shell surface 10' and the recess 4 are perpendicular, so that gravity and centrifugal force optimally support emptying. The recesses 4 themselves can also be conical, as not shown here; in this case the bisector of the conical recess in the cross section should be positioned vertically. Otherwise, this device corresponds to the one shown in Figure 4.

For very slow rotating designs, the higher manufacturing costs of the conical design presented above are not worthwhile; however, at high speeds, particularly above about 40 revolutions per minute, its advantages become increasingly apparent. The higher the intended speed, the greater the optimal cone angle £> . As the cone angle increases, the movement of the conveyed material 2, initially presented as an axial movement, increasingly changes into a radial movement.

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If this development direction were to be continued up to its extreme shown in Figures 10 and 11, the movable part 3 would ultimately become a ring. The after-aperture 8 would then also have to be ring-shaped in a concentric arrangement outside the movable part 3. The front-aperture 5 would have to be arranged concentrically radially inside the movable part 3. However, the inclination @ of the rotation axis 13 relative to the vertical cannot be driven arbitrarily far, firstly because this is not necessary to support emptying in the case of large centrifugal forces and secondly because filling the recesses 4 would then become unnecessarily difficult; therefore, in this extreme version, the rotation axis 13 is again set vertically.

In this design, the main conveying direction H remains vertical in front of the pre-orifice 5. However, it (H) is gently diverted into the radial direction in the pre-orifice 5, which is larger for this purpose. The main conveying direction K is therefore radial both at the interface between the pre-orifice 5 and the movable part 3 and at the interface between the movable part 3 and the post-orifice 8.

The movement of the movable part 3 and - if these are also moved - of the two apertures 5 and 8 takes place in the circumferential direction around a vertical axis 13, preferably as a continuous rotary movement. Since the circumferential direction is perpendicular to the radial, this design also fulfills the inventive feature that the main conveying direction H and the relative movement between the apertures and the movable part are perpendicular to one another; this also makes jamming particularly unlikely.

Because in this variant of the dosing device - due to the movement in a horizontal plane - gravity cannot be used as a propulsion means, especially at the after-diaphragm 8, it is recommended in this variant to also rotate the two diaphragms 5 and 8 in order to provide a propulsion means with the centrifugal force thus created. As already written earlier, the rotational movement of the two 31s, the 5 and 8, should be synchronous and so phase-shifted that their pre- and after-holes never coincide; this makes it easy to ensure that phases I and III do not overlap. In order to increase the centrifugal force effect desired here, the rotational movements of the diaphragms 5, 8 on the one hand and the moving part 3 on the other hand preferably match in their direction of rotation and only differ from each other in the amount of the speed by 0 to preferably only 20%, depending on the required dosing flow.

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In this version, the front aperture 5 has only one front hole 7 and the rear aperture 3 only one rear hole 9. In contrast, the middle, movable part 3 has five recesses 4, of which only two are shown in dashed lines so as not to overload the image.

Figure 12 shows a schematic cross-section of a sand washing plant with a metering device 1 according to the invention for the controlled removal of sufficiently cleaned sand 2. The sand present in the wastewater usually has a more or less thick shell of organic substance adhering to each silicate grain. A sarcoma with its shell is referred to below as an aggregate. The organic substance has a lower specific weight than the silicate, so that it reduces the specific weight of the aggregate.

The separation of sand that has been cleaned to such an extent that it no longer needs to be disposed of at great expense but can be used without any problems in the construction industry and possibly even in the glass industry is carried out in two steps, which are usually carried out alternately several times in succession or simultaneously:

Firstly, a sharp pump jet 18 introduced onto the surface and/or a fast agitator 19 acting on the surface or even two agitators arranged concentrically in opposite directions create a flow state of strong shear, which causes the softer organic shell to be ground away from the harder silicates.

Since each silicate grain is shaped differently and has a slightly differently composed and sized organic shell, there are some sand grains that are quickly freed of their disturbing organic shell and others for which this takes longer - in order to minimize the appearance that already clean sand grains still needlessly go through the washing process, secondly, the layer of the heaviest (i.e. the cleanest) sand that settles at the bottom is kept reasonably thin, that is, excess clean sand is drawn off downwards by a dosing device. ■!. The layer of pure sand must not be too thin, however, on the one hand because its top layer performs a certain filter function and on the other hand because cleaned, sharp-edged sand acts as a kind of cleaning brush and polishing cloth for the sand that still needs to be cleaned, so that if too much clean sand is drawn off, the residual sand cleaning becomes less effective. From extensive experience, the applicant now knows the optimal sand layer structure.

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If the sensors 15 now detect that the pure sand layer is too thick, the motor 14 is activated, which causes the movable part 3 to rotate and thus transports sand from the bottom layer out of the basin 16. As soon as the sensor 15 detects that the lower tolerance limit for the layer thickness of the pure sand has been reached or a simple time relay has caused the motor 14 to be switched off, the movable part 3 comes to a stop in any random position. Because the lack of relative movement prevents the dosing device 1 from expelling further sand 2 in any position, the minimum required sand layer thickness is always maintained.

The invention is not limited to the embodiments shown; rather, all obvious modifications of the same and the claims are included. For example, to minimize the consequential damage of a seal failure, the motor 14 can be arranged above the moving part 3 instead of below it, in particular above the level of the conveyed material 2, so that no conveyed material, for example sludge, can penetrate into the motor 14. It all depends on

- that the movable part 3 - and/or, in kinematic reversal, the orifices 5 and 8 - moves or move essentially perpendicular to the main conveying direction H, as it (H) is shown on the sealing sliding surface&trade;, between the front orifice 5 and the movable part 3 on the one hand and between the movable part 3 and the rear orifice 8 on the other hand, and that

- that between the orifices 5, 8 on the one hand and the "moving part" 3 on the other hand, the relative movement Q can be set to represent the dosing flow (= delivery flow) 0 and a relative speed deviating from 0 to represent a real dosing flow, and that

- that both panels 5, 8 and the movable part 3 have openings such that the openings of adjacent parts (5 and 3 or 3 and 8) can at least partially coincide, but never all three parts at the same time.

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List of reference symbols

1 device for dosing 2

2 Material to be conveyed (bulk material or pasty mass)

3 moving part of 1

4 recesses in 3

5 Cladding

6 cases of 1

7 pre-holes in 5

8 After-fade

9 holes in 8

10 Surface area of 3

11 upper face of 3

12 lower front face of 3

13 Rotation axis of 3

14 Engine

15 Sensor for detecting sand stratification"

16 pools

17 Clamping screws for fixing the panels 5 and 13 Pump jet for sand washing IS agitator

20 sand silo

21 funnel

22 State-of-the-art dosing device

23 roll of 22

24 recesses in 23

25 housings

2 6 Sealing gap between 23 and 25

d Thickness of the moving part

k largest grain size of 2

w4 smallest width of a recess

w7 smallest width of a pilot hole

w9 smallest width of a post hole

V Vertical

H Main conveying direction W4 largest width of a recess W7 largest width of a pre-hole 7 W9 largest width of a post-hole

ß Cone angle

@ Angle between V and 13' μ Phase shift between apertures 5 and

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RENTEC dosing device * &Ggr; .*

Phase range of a recess A, in which it (4) at least partially overlaps with a pre-hole (7) so that conveyed material (2) penetrates into the recess (4)
II- Phase range of a recess 4 in which it (4) does not overlap (not even partially) with a pre-hole (7) so that no conveyed material (2) penetrates into the recess (4)

III Phase area of a recess 4, in which it (4) at least partially overlaps with a post hole (9)/ so that conveyed material (2) can be removed from the recess

(4) emerges

IV Phase range of a recess A in which it (4) does not overlap (even partially) with a post-hole (9) so that no conveyed material (2) can escape from the recess (4)

Claims (19)

Protection claims Device (1) for dosing bulk materials (2) or pasty masses (2), which includes a movable part (3) with one or more recesses (4), whereby the thickness (d) of this movable part (3) is greater than the largest grain size (k) of the conveyed material (2) and wherein this thickness (d), the number and size of the recesses (4) and the speed of the movable part (3) influence the discharge speed (=dosage) of the conveyed material (2), characterized in that a) it (1) contains three parts (5, 3 and 8) arranged in succession in the conveying direction, of which the first part, referred to as the front baffle (5) and the third part, referred to as the rear baffle (8), can be moved perpendicularly to the main conveying direction (H) and/or the middle part (3), which is referred to below as "movable part (3)" (even if it is immobile in one variant), whereby b) the pre-aperture (5) has one or more recesses referred to as "pre-holes" (7) in such an arrangement that during a movement cycle of the movable part (3) opposite the 3 ends (5 and S) at least one pre-hole (7) and one recess (4) of the movable part (3) overlap at least partially in one phase region (I) and do not overlap at all in another phase region (II+III+IV), and that c) the after-diaphragm (8) has one or more recesses referred to as "after-holes" (9) in such an arrangement that during a movement cycle of the movable part (3) relative to the diaphragms (5 and 8), at least one after-hole (9) and one recess (4) of the movable part (3) at least partially overlap in a phase range (III) and do not overlap at all in another phase range (IV+I+II), whereby d) the phase regions (I) and (III) do not overlap at any time, so that at any time it is impossible for each recess (4) of the movable part (3) to be open to both a pre-hole (7) and a post-hole (9). RENTEC dosing device·'.":· j · :«Series:t£*2 2. Device according to claim ₁₇ , characterized in that the direction of movement of the movable part (3) deviates by at least 50 degrees from the main conveying direction (H). 3. Device according to claim 2, characterized in that the direction of movement of the movable part (3) deviates by at least 80 degrees from the main conveying direction (H). 4. Device according to one of the preceding claims, characterized in that the movable part (3) is periodically moved back and forth when the material to be conveyed is dispensed. 5. Device according to one of the preceding claims, characterized in that the movable part (3) rotates or is rotated continuously when the material to be conveyed is discharged. 6. Device according to one of the preceding claims, characterized in that the movable part (3) has a lateral surface (10) of conical shape with a cone angle (ß) between the axis of rotation (13) and the lateral surface (10). ■7. Device according to claim 6, wherein the cone angle (ß) is preferably less than or equal to 20 degrees, characterized in that the axis of rotation (13) of the movable part (3) is inclined by an angle (@) with respect to the vertical (V), wherein the angle of inclination (@) is approximately equal to the cone angle (ß). .8. Device according to claim 5, preferably according to claims 6 or 7, characterized in that at least one of the end faces (11, 12) of the movable part (3) is conical, preferably with the complementary cone angle· (90 degrees - ß). 9. Device according to claims 6 and 8, characterized in that the "cone" angle (ß) is 90 degrees, so that the movable part (3) and the after-aperture (8) are rings arranged concentrically around the front-aperture (5). 10.Device according to one of the preceding claims, characterized in that each pre-hole (7) in the pre-diaphragm (5) is smaller than each recess (4) in the movable part (3) and that each post-hole (9) in the post-diaphragm (8) is larger than each recess (4). RENTEC dosing device »"j "\· ··■ :**gej;{:^ "5"· 11.Device according to claim 10, characterized in that both the largest and the smallest width j (W7, w7) of each pilot hole (7) is smaller than the &igr; largest or smallest width (W4, w4) of each Recess (4) and that both the largest and - ] the smallest width (W4 , w4) of each recess '. (4) is smaller than the largest or smallest width (W9, w9) of each post hole (9). 12. Device according to claim 10 or 11, characterized in that each pre-hole (7), each recess (4) and each post-hole (9), insofar as they (7, 4, 9) are located in a common movement track, are of similar shape. 13.Device according to one of the preceding claims, characterized in that the pre-diaphragm (5) and/or the post-diaphragm (8) is excited to oscillate with a small amplitude CA), preferably less than 20 degrees in the case of rotary oscillation. 14.Device according to one of the preceding claims, characterized in that the pre-diaphragm (5) and the post-diaphragm (S) are moved synchronously, i.e. with a phase offset (μ) that is constant over time, preferably rotationally. 15.Device according to claim 14, characterized in that in kinematic reversal of the movement sequence described in claims 1 to 12, the two diaphragms (5 and 8) essentially move, while the "movable" part (3) located between them either does not move at all or at most oscillates with a small amplitude (A) according to claim 12. 16.Device according to claim 14, characterized in that both diaphragms (5 and 3) as well as the movable part (3) located between them move, wherein both movement speeds are different from one another. .Device according to claim 16, characterized in that both movement speeds are approximately equal in magnitude, but are oriented in opposite directions. 18.Device according to one of the preceding claims characterized in that in the end face pairing between the front panel (5) and the movable part (3) as well as between the movable part (3) and the rear panel (8) the material pairing metal/metal is avoided, preferably is designed as metal/plastic or plastic/plastic. RENTEC dosing device 19. Device according to one of the preceding claims characterized in that it is used for the metered discharge of a material (2) deposited on the bottom of the basin from a wastewater treatment plant.