EP4433392A1

EP4433392A1 - Gravimetric metering unit

Info

Publication number: EP4433392A1
Application number: EP22826192.1A
Authority: EP
Inventors: Men BERNEGGER; Rolf Lehmann; Urs Helfenstein
Original assignee: K Tron Technologies Inc
Current assignee: K Tron Technologies Inc
Priority date: 2021-11-15
Filing date: 2022-11-14
Publication date: 2024-09-25
Also published as: CN118574780A; CH719146A1; WO2023084480A1

Abstract

The invention relates to a gravimetric metering unit for bulk material, comprising a metering means (2) having a container (8) for bulk material to be metered and a base unit (4), wherein the base unit (4) has a conveyor channel that feeds into an outlet line of the metering unit (1) via a connection device having a flexible sealing element, and wherein, via the connection device, the conveyor channel can be operationally connected to the outlet line and detached from same, wherein the connection device has a magnetic securing arrangement for the operational connection of the sealing element at least to either the outlet line or the conveyor channel or to both.

Description

Gravimetric dosing unit

The present invention relates to a gravimetric dosing unit for bulk materials according to the preamble of claim 1.

The gravimetric feeders, also known as loss-in-weight feeders, are widespread and used in many branches of industry for all kinds of flowable or pourable materials, i.e. bulk goods, insofar as these can be conveyed at all by a gravimetric feeder. In this case, the pourable materials are discharged into a container, from this into a base unit located below it and metered out by a conveyor present in the base unit from the dosing device into an output channel. The doser is on a scale, so the weight registered by the scale is the gross weight, i.e. the known and constant weight of the components of the doser (tare) plus the variable weight of the bulk material actually present in the container and in the base unit (net weight).

In this way, the scales continuously register the weight loss of the entire feeder during operation of the feeder, and thus the weight loss of the bulk material in the feeder due to the constant weight of the feeder, so that a control of the feeder can determine the output actual mass flow of the pourable material from the weight loss and in comparison with a predetermined desired mass flow rate, the output conveyor can be regulated accordingly in order to minimize the difference between the actual and the desired mass flow rate.

A very precise regulation of the output mass flow can be necessary, for example in the pharmaceutical sector or if color pigments are to be mixed in in industrial production. In addition, the target mass flow can be small, for example in the case of the color pigments mentioned and in the manufacture of medicines (e.g. less than 1 kilogram per hour), or large, for example in the field of plastics production and in mining (e.g. more than 1 1 per hour). precise dosing may be necessary even with such delivery rates. Furthermore, different batches can be run one after the other, in which case, depending on the bulk material, an additional intensive cleaning may be necessary in addition to the regular maintenance. Precise scales of all kinds are often used as scales, with a resolution over their weighing range of 1:100,000 and more, including those with vibrating wire sensors, such as those under the designation SFT-III, SFT-II-M and SFT-II- Lvon Coperion K-Tron are known. These scales have a resolution of up to 1:4000000, so that precise dosing can be carried out without any problems even with a container content of several hundred kilos and a conveyance of several tons per hour. If, for example, a resolution of 1:1,000,000 is used, the weight can still be recorded with an accuracy of 1/10 g and then used for dosing with a weighing capacity of 100 kg.

In order to use the precision of the scales for dosing, the connection to the output channel must be designed in such a way that no forces with components in the weight direction of the dosing device are transmitted to the dosing device from the output channel, otherwise the scales would measure such forces in addition to the actual weight loss and the controller would use an incorrect weight change of the metering device to control the actual mass flow.

Frequently, conveyors that are not vertical, i.e. horizontal or arranged at an angle, are preferably used, as this allows the fluid-dynamic behavior of the bulk material to be controlled somewhat better, since, among other things, in the case of horizontal conveyors, gravity does not act in the conveying direction and thus does not influence the flow of the bulk material. Longer screw conveyors, for example, are well suited as horizontal conveyors, since with a suitable drive, the actual delivery rate can be varied quite easily and without delay via their speed and the distance from the mass flow from the hopper to a collection container outside the dosing unit can be easily bridged. without any disadvantages arising in the actual mass flow itself. Frequently, such conveyors are clamped in a metering device of the type mentioned on an end shaft in a holder, the holder supporting the conveyor in an exactly aligned manner in its conveyor pipe, which thus forms a conveyor channel.

For the connection of the delivery channel to the delivery line, a connecting device is often provided which has a flexible sealing element which, due to its mobility, allows relative movements between the delivery channel (and thus the metering device) and the delivery line, thereby decoupling the metering device from forces from this relative movement. Depending on the type of scale used, these relative movements can be very small, but they are still relevant. Since the connecting device is suitable for the bulk materials mentioned above has to be, it is designed to be dust-tight, for example, ie usually connected to the conveying channel and to the delivery line via a screw connection having seals or via clamping rings. As mentioned above, the flexible sealing element (and the entire connecting device) must be cleaned or replaced when changing batches or when dealing with sensitive bulk goods.

If several dosing units are grouped like spokes around a common output line, as is shown, for example, in the "K-Tron Product Information K4G Continuous Gravimetry Blender / K4G-L Group" brochure, cramped conditions arise at the location of the output line in addition to the design-related, quite high maintenance effort , some of which are difficult to access for a fitter and thus increase the maintenance time, so that additional space for maintenance work must therefore often be provided even when the dosing unit is being built.

Accordingly, it is the object of the present invention to provide a dosing unit or a conveying arrangement for a dosing device that saves maintenance time and can be easily assembled and disassembled even in confined spaces.

This object is achieved by a dosing unit having the characterizing features of claim 1.

Because a magnetic connection is provided, the known detachable connections such as screw connections etc. are no longer necessary, with the result that there is no space for the tool to be attached (and the necessary movements of the tool) - in addition, there is no time for fastening and loosening of the connections, because a magnetic connection ultimately represents a snap connection that can be released with a slight tug somewhere at the back of the dosing device and, when brought back into position, snaps in by itself.

Further preferred embodiments have the features of the dependent claims.

The invention is described in more detail below with reference to the figures.

It shows: Figure 1 shows a dosing unit of the prior art,

FIG. 2 shows an embodiment of a dosing unit according to the invention, and

FIG. 3 shows a view of the bellows with the fixing rings.

FIG. 1 schematically shows a gravimetric dosing unit 1 of the prior art for bulk materials of the type mentioned above.

In operation, the hopper 3 is filled with bulk material, which falls here via a transfer hopper 7 (which can also be omitted) of the base unit 4 into a conveyor container 8, through which a conveyor screw 9 protrudes, which conveys the bulk material from right to left into a discharge line 10 promotes, via which the bulk material arrives in a further conveyor section 11, indicated by dashed lines, for further processing. The funnel is refilled before empty.

In addition to the delivery container 8, the base unit 4 comprises a drive motor 12 with a gear 13, the conveyor screw 9 driven thereby, which in turn is placed on the mandrel of a holder 14 and runs after the delivery container 8 through a delivery channel 15, which also belongs to the base unit, to the output line 10. The base unit 4 or the conveying channel 15 is mechanically decoupled from the dispensing line 10 via a flexible sealing element, here designed as a bellows 17, which also completely seals powdery bulk materials, so that the weighing of the dosing unit 2 cannot be influenced by the dispensing line 10. The bellows 17, together with the associated screw connection on the delivery line 10 and on the delivery channel 15, forms a connecting device 17 for the delivery channel 15 with the delivery line 10.

The feeder 2 rests on the supports 19 on the scales 5, which register the weight of the feeder 2 and the weight of the bulk material in the hopper 3 (and in the base unit 4). If, in gravimetric operation of the dosing unit 2, bulk material is discharged into the further conveying section 11 by the rotation of the screw conveyor 9, its weight is reduced accordingly, which is registered by the scales 5 and in turn evaluated by a controller (not shown) to relieve the figure. The weight reduction responds to the output actual mass flow of bulk material, which must be tracked to the target mass flow. For this purpose, the control via the drive motor 12 continuously corrects the speed of the conveyor screw 9 in accordance with a control algorithm that is fundamentally known to the person skilled in the art.

If, for example, several dosing units 1 are grouped around the dispensing line 10 that they share, the maintenance or cleaning of the bellows 16 must be carried out from the right side, past the motor 12, the delivery container 8 and the delivery channel 15, which is tedious and, above all, the The use of tools is made more difficult, especially when the space available at the location of the bellows 16 is tight.

FIG. 2 shows a view of part of the base unit 20 of a dosing unit according to the invention, which corresponds to the dashed area 18 of the dosing unit 1 of FIG. One third of the components shown have been cut away, so that the upper half is shown in cross-section (the cutting plane lies in the plane of the drawing) and the lower half in a section running diagonally from below, so that the cutting plane is inclined at about 30 degrees to the plane of the drawing.

A conveying container 21 can be seen, through which a conveying screw 22 protrudes, which after the conveying container 21 further to the left through a conveying channel 23 extends to a delivery line 24, into which it in turn protrudes freely and thus without contact. During operation, the conveyed bulk material passes from the conveying container 21 via the rotating conveying screw 22 to the left into the discharge line 24, where it falls down into the further conveying path 11 (FIG. 1), not shown in FIG.

According to the invention, the connecting device 17 has a flexible sealing element, which is designed as a bellows 25 in the embodiment shown, as well as a connecting piece 26 and a carrier 27 for the bellows 25. Instead of a bellows, the person skilled in the art can also use another suitable flexible connection in the specific case provide, instead of a separate carrier 27, for example in a short conveyor channel, the wall of the delivery container 21 (or another component of the metering device 2 of Figure 1) can be designed as a carrier. Likewise, for example, the connecting piece can be formed by the output line 24 itself, depending on the design of the base unit 4 in the specific case. It should be noted at this point that FIG. 2 also shows that in one embodiment the conveying channel 23 is arranged horizontally. FIG. 2 also shows how the conveying channel 23 protrudes in the conveying direction (ie from right to left towards the discharge line 24 in the figure) beyond the bellows 25 or the flexible sealing element, so that bulk material discharged from it directly into the discharge line 24, at best falls into the socket 26, but not into or onto the bellows 25. Bulk material falling onto the bellows 25 would burden it with the impact and the weight of its mass, whereby these forces would necessarily also act on the carrier 27 supporting the bellows 25 , with the result that the scales 5 (Figure 1) registered additional weight, which falsified the dosing of the bulk material. The connecting device 17 is thus designed in such a way that the bulk material that is dispensed cannot impair the weight measurement by the scales 5 and thus the gravimetric dosing of the bulk material. The end of the sealing element that faces the discharge line (24) is therefore preferably in the conveying direction at or behind the end of the conveying channel (23) that faces the discharge line (24), such that the flow of bulk material discharged from the conveying channel (23) during operation does not reach the sealing element .

A magnetic fastening arrangement 28 provided in the connecting device 17 ensures the detachable and reconnectable connection of the flexible sealing element or bellows 25 with the dispensing line 24 on the one hand (via the outlet connector 26) and on the other hand the delivery channel 23 (via the carrier 27). The magnetic fastening arrangement 28 now has, on the one hand, a mechanical position arrangement 29 for mechanically positioning the bellows 25 in the connecting device 17 in its operating position and, on the other hand, a magnetic fixing arrangement 30 for magnetically fixing the bellows 25 in its (mechanically given) operating position.

The mechanical position arrangement 29 has stop elements on the bellows 25 and stop elements of opposite design on the outlet nozzle 26 and on the carrier 27 . In the embodiment shown, the stop elements on the bellows 25 are designed as openings 31, 31', the stop elements of opposite design as magnets with the geometric shape of positioning pins (whereby the magnetic property is irrelevant for the mechanical position arrangement), so that the stop elements of opposite design here positioning magnets 32,32' are arranged on the outlet nozzle 26 and on the carrier 27 and mechanically engage in the openings 31,31'. The openings 31,31' are located in fastening sections of the bellows 25, here in a radially projecting flange 33,33'. However, the fastening sections can also be designed as tongues which are suitably arranged on the flexible sealing element and have the openings, but other suitable areas of the flexible sealing element can also be provided as fastening sections. It turns out that the flexible sealing element has fastening sections with openings for positioning pins. It also results that the fastening sections are preferably designed as a flange projecting radially from the bellows, with a flange being provided at least at one end or at both ends of the bellows. FIG. 3 shows the bellows 25 of FIG. 2 in detail.

In addition, the mechanical position arrangement 29 preferably has stop elements on the flexible sealing element and further stop elements of opposite design to the stop elements on a connecting piece 26 arranged on the dispensing line or on a carrier 27 arranged on the base unit 4, which determine the operational relative position of the flexible sealing element at the connection piece 26 or at the carrier 27.

It should be noted at this point that "opposite" does not necessarily mean complete congruence of the interacting stop surfaces. It can be seen from FIG. 2 that the positioning magnets 32, 32′ position the bellows 25 exactly radially, while the exact angular position of the bellows is less critical. Correspondingly, the openings 31,31' can also be in the form of oblong holes, since the ferromagnetic ring 34,34' adheres equally well to the positioning magnets 32,32' in any angular position. "Opposite" means that the stop surfaces are completely the same (congruent) or at least as far as is necessary for proper operative positioning depending on the specific design of the magnetic fastening arrangement 28 .

In addition to the positioning magnets 32, 32', which are each arranged, e.g. glued, in the connecting piece 26 and in the carrier 27, the magnetic fixing arrangement 30 has a magnetic ring 34, 34', which is designed, for example, as a ferromagnetic ring and is connected to the positioning magnets 32 ,32' interacts magnetically. However, the ring 34, 34' can also consist of a plastic fitted with magnets or another non-magnetic material. In the embodiment shown in FIG. 2, the positioning magnets 32, 32' have a mechanical function (positioning, see above) and a magnetic function by attracting the magnetic ring 34,34' and thus fixing it in its position.

As a result, each ring 33,33' held in place by the magnets 32,32' encloses a flange 34,34' of the bellows 25 between itself and the connecting piece 26 or the support 27, so that it cannot be separated from the connecting piece 26 or the support 27 can be lifted off, ie fix the flange 34,34' and thus the bellows 25 in its relative (predetermined by the stop elements) position to these in an operable manner. In the present description, operable means that the intended function can be maintained under all circumstances occurring during operation of the dosing unit, such as movements or bulk materials used, etc. Thus, the ring 34, regardless of its specific design, represents a magnetically effective fixing element that can be designed as a fixing ring or in another suitable form. Figure 3 shows the bellows 25 and magnetic rings 34 of Figure 2 in detail

With the ferromagnetic rings 34,34' there is a magnetic active area on the bellows 25, and with the positioning magnets 32,32' there is an oppositely arranged magnetic active area on the outlet connection 26 or carrier 27, with these magnetic active areas interacting.

The result is that the magnetic fixing arrangement 30 preferably has a magnetic effective area on the flexible sealing element (designed here as a bellows) and a magnetic effective area arranged in opposite directions (in terms of its position) on a connecting piece 26 arranged on the output line 24 or on a connecting piece 26 on the base unit 4 arranged carrier 27, which effective areas fix the operative relative position of the flexible sealing element on the connecting piece 26 or on the carrier 27 in an operative manner.

In the embodiment shown in FIG. 2, the positioning magnets 32,32' act on the one hand as stops for the openings 31,31' and on the other hand as magnets which fix the magnetic ring 34,34'. It follows that the one magnetic effective area is preferably formed by positioning pins designed as magnets, in the embodiment according to FIG. 2 by the positioning magnets 32, 32'. FIG. 3 shows the bellows 25 and the magnetic rings 34,34' in the manner of an exploded drawing, the connecting piece 26 and the carrier 27 (FIG. 2) being omitted to make the figure lighter, but the position of the positioning magnets 32,32' ( Figure 2) is indicated by the dashed lines 35,35'. When assembled, ring 34 is internal to flange 33 and ring 34' is internal to flange 33' as indicated by the dashed arrows. Each ring 34,34' preferably has handles 36,36'. It turns out that the fixing element designed here as a fixing ring (34, 34') preferably has handles (36) and is particularly preferably designed to be ferromagnetic. However, as mentioned above, it can also be made of a non-magnetic material, for example, and have magnets or ferromagnetic material.

In this way, with an operationally assembled dosing unit 1 with a base unit 4 configured, for example, according to FIG or work and without wasting time.

If the dismantled base unit 4 is to be reconnected to the output line 26, the bellows 25 can simply be slipped onto the positioning magnets 32' on the carrier 27 and the ring 34 placed on them, whereby the bellows is fixed in the correct position on the carrier 27. The base unit 4 is then brought into the operative position along its longitudinal direction from right to left, whereupon the fitter simply feels his hand behind the delivery container 21 against the connecting piece 26 and there grasp the loose ring 34 on the handles 36 between his thumb and fingers and can be placed on the connecting piece 26 - the openings 31 are already located at the location of the positioning magnets 32, since the flange 34' has already been correctly positioned by the positioning magnets 32'. There is no need for tools, this manipulation requires comparatively little space, so that the cramped conditions are irrelevant. The time required is also negligible.

In a further embodiment not shown in the figures, the bellows 25 or the flexible sealing element is only provided with a magnetic fastening arrangement on one side, while the other side is conventionally fastened to the connecting piece or to the carrier. It is then advantageous that the base unit 4 can be detached (or mon- animal) can be, the conventional attachment to the remote base unit 4 is then easier and faster detachable or connectable. Conversely, if the conventional attachment is on the side of the connecting piece, the flexible sealing element can also be dismantled or assembled more easily, since the dismantled base unit is no longer in the way and there is therefore less cramped space.

In a further embodiment not shown in the figures, the mechanical position arrangement and the magnetic fixing arrangement are separate from one another, so that the stop elements are not magnetically effective.

However, as in the case of the positioning magnets 32, 32', it is then preferred that the stop elements have positioning pins and the stop elements of opposite design have openings of opposite design to the positioning pins, and more preferably the stop elements have openings provided in the flexible sealing element and the stop elements of opposite design Have positioning pins that are fixed relative to the connecting piece 26 or the carrier 27.

Regardless of whether the mechanical position arrangement and the magnetic fixing arrangement are separate from one another, it is preferred that the flexible sealing element has fastening sections and the magnetic effective area on the flexible sealing element is formed by at least one magnetic fixing element, which in the operating position has the fastening sections between itself and either the Connection piece or the carrier includes and thus fixes the flexible sealing element in an operative position operable, wherein the fixing element is in turn held magnetically in its position.

In the embodiment shown in FIG. 2, the positioning pins designed as magnets are arranged at least either on the connecting piece 26 or on the carrier 27 or on both, and can be pushed out from one side through the openings 31, 31′ provided on the flexible sealing element. for the positioning pins and further on the other side of the openings 31,31' at least one magnetic fixing element is provided, which encloses the fastening sections of the flexible sealing element between itself and the connecting piece 26 or between itself and the carrier 27 and magnetically fixes it to the magnet in turn fixed the flexible sealing element in operative stock. The figures do not show an embodiment in which, instead of the connecting piece 26 or the carrier 27, the fixing ring or the fixing element which has the magnetic positioning pins and then, for example, the connecting piece 26 or the carrier 27 consist of a ferromagnetic material, and openings for the Have positioning pins.

It is then preferable for the positioning pins designed as magnets to be arranged on the fixing element and to extend from one side through the openings for the positioning pins provided on the flexible sealing element and for magnetically effective openings to be provided in the connecting piece or the carrier on the other side wherein the fixing element encloses the fastening sections of the flexible sealing element between itself and the connecting piece or the carrier and magnetically fixed at the openings in turn fixes the flexible sealing element in an operative position.

It is different if, as mentioned above, the mechanical location arrangement and the magnetic fixation arrangement are separated from one another, so that the stop elements are not magnetically effective. Then, for example, on the connecting piece 26 or on the carrier 27, magnets can be arranged separately from the stop elements, which interact with a ferromagnetic fixing ring or fixing element or one that is itself equipped with magnets. Cider, the connecting piece 26 or the carrier 27 are ferromagnetic and interact with magnets arranged on the fixing element.

The result is that the magnetic fixing arrangement then preferably has magnets that are separate from the mechanical position arrangement and are arranged in the connecting piece or in the carrier, and the fixing element is designed to be magnetically active, and this is between itself and the connecting piece or between itself and the carrier Includes attachment portions of the flexible sealing element and magnetically fixed to the magnet in turn fixes the flexible sealing element in operative stock.

Common to all of the described embodiments is a gravimetric dosing unit for bulk goods, which has a dosing device 2 with a container 8 for bulk goods to be dosed and with a base unit 4, with the base unit 4 having a conveying channel which, via a connecting device having a flexible sealing element, leads into a discharge line the dosing unit opens out 1, and wherein via the connecting device the conveying channel can be operatively connected to the dispensing line and detachable from it again, wherein the connecting device also has a magnetic fastening arrangement for the operative connection of the sealing element at least to either the dispensing line or the conveying channel or to both.

Claims

patent claims

1. Gravimetric metering unit for bulk materials, with a metering device (2) having a container (8) for bulk material to be metered and a base unit (4), wherein the base unit (4) has a conveyor channel (23) which has a flexible Connecting device (17) having a sealing element opens into a dispensing line (24) of the dosing unit (1), and wherein via the connecting device (17) the conveying channel (23) can be operationally connected to the dispensing line (24) and can be detached from it again, characterized in that in that the connecting means (17) comprises a magnetic fastening arrangement (28) for the operative connection of the sealing element to at least one of the discharge conduit (24) and the conveying channel (23) or both.

2. Gravimetric dosing unit according to claim 1, wherein the magnetic fastening arrangement (27) comprises a mechanical positioning arrangement (29) for positioning the flexible sealing element in the connecting device (17) in its operating position and a magnetic fixing arrangement (30) for magnetically fixing the flexible sealing element in the operating position.

3. Gravimetric dosing unit according to claim 1, wherein the mechanical position arrangement (29) has stop elements on the flexible sealing element and further stop elements of opposite design to the stop elements on a connecting piece (26) arranged on the dispensing line or on a carrier (27 ) which determine the operative relative position of the flexible sealing element on the connection piece (26) or on the carrier (27).

4. Gravimetric dosing unit according to claim 3, wherein the stop elements have positioning pins and the stop elements of opposite design to the positioning pins have openings of opposite design Gravimetric dosing unit according to claim 3, wherein the stop elements have openings provided in the flexible sealing element and the stop elements of opposite design have positioning pins which are fixed relative to the connecting piece or the carrier. A gravimetric dosing unit according to claim 4, wherein the flexible sealing element has attachment sections with openings for positioning pins. Gravimetric dosing unit according to Claim 1, in which the flexible sealing element is designed as a bellows (25). Gravimetric dosing unit according to Claims 6 and 7, in which the fastening sections are designed as flanges (33, 33') projecting radially from the bellows, with a flange (33, 33') at least on one end or on both ends of the bellows (25, 25' ) is provided. Gravimetric dosing unit according to claim 2, wherein the magnetic fixing arrangement (30) has a magnetic effective area on the flexible sealing element and a magnetic effective area arranged in opposite directions on a connecting piece (26) arranged on the dispensing line or on a carrier (27) arranged on the base unit (4). , which effective areas operatively fix the operative relative position of the flexible sealing element on the connecting piece (26) or on the carrier (27). Gravimetric dosing unit according to claim 9, wherein the flexible sealing element has fastening sections and the magnetic effective area on the flexible sealing element is formed by at least one magnetic fixing element which, in the operating position, encloses the fastening sections between itself and either the connecting piece or the carrier and thus the flexible sealing element in the operative position operatively fixed, the fixing member in turn being magnetically held in position. Gravimetric dosing unit according to claims 4 and 9, wherein the one magnetic effective area is formed by positioning pins (32, 32') designed as magnets.

12. Gravimetric dosing unit according to claim 11 and 6, wherein the positioning pins (32,32') designed as magnets are arranged at least either on the connecting piece (26) or on the carrier (27) or on both, extending from one side through the am flexible sealing element provided openings (31,31') for the positioning pins (32,32') extend through and further on the other side of the openings (31,31') at least one magnetic fixing element is provided, which between itself and the connecting piece (26 ) or between itself and the carrier encloses the fastening sections of the flexible sealing element and magnetically fixed to the magnet, in turn, fixes the flexible sealing element in an operative bearing.

13. Gravimetric dosing unit according to claim 11 and 6, wherein the positioning pins designed as magnets are arranged on the fixing element and extend from one side through the openings for the positioning pins provided on the flexible sealing element and further on the other side magnetically effective openings in the Connection supports or the carrier are provided, with the fixing element enclosing the fastening sections of the flexible sealing element between itself and the connection piece or the carrier and magnetically fixed at the openings in turn fixing the flexible sealing element in operative storage.

14. Gravimetric dosing unit according to claim 3, wherein the magnetic fixing arrangement has magnets which are separate from the mechanical position arrangement and which are arranged in the connecting piece or in the carrier, and the fixing element is designed to be magnetically effective, and wherein this is between itself and the connecting piece or between itself and the Carrier includes the attachment portions of the flexible sealing element and magnetically fixed to the magnets in turn fixes the flexible sealing element in operative stock.

15. Gravimetric dosing unit according to claim 10 or 12, wherein the magnetic fixing element is designed as a ferromagnetic ring (34, 34').

16. Gravimetric dosing unit according to one of claims 10 or 12, wherein the fixing element has magnets.

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17. Gravimetric dosing unit according to one of claims 10 or 12, wherein the fixing element, which is preferably designed as a fixing ring, has handles (36) and is particularly preferably designed to be ferromagnetic.

18. Gravimetric dosing unit according to claim 1, wherein the conveying channel (23) is arranged horizontally.

19. Gravimetric dosing unit according to claim 1 or 18, wherein the end of the sealing element facing the dispensing line (24) is located in the conveying direction at or behind the end of the conveying channel (23) facing the dispensing line (24), such that during operation the end of the conveying channel (23) the discharged bulk material flow does not reach the sealing element.

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