Metering device for variably metering powder

Abstract

The invention relates to a powder metering device (10) for variably metering powder quantities, having a metering chamber (1) with a defined metering volume, said metering chamber being connected, on the inlet side, to a powder feed line (2) and, on the outlet side, to a discharge line (4) to which negative pressure can be selectively applied, wherein the metering chamber (1) is formed by a line portion (5) having an inlet valve (6), an outlet valve (7) lying opposite thereto, and an interposed ventilation valve (8), and a control unit (41) of the device (10) is designed to selectively control the valves (6, 7, 8) for a preferably variable metering process in the line portion (5).

Description

[0001] Dosing device for variable dosing of powder

[0002] The present invention relates to a dosing device and a powder dosing method, wherein powder can be variably conveyed through a dosing chamber with a predefined volume by means of negative pressure.

[0003] Devices and systems for dosing powder or powdered substances in the industrial sector are well known. Common devices for dosing powdered substances or media are often designed in such a way that determining the delivered quantity is comparatively cumbersome and can only be carried out with relative accuracy. This is particularly true for dosing systems for smaller quantities, such as those required in the chemical industry or, for example, in battery manufacturing. In particular, the required consistency in measuring or dosing the quantities is difficult to guarantee with these devices. Deviations and thus inaccurate dosing are common, which can lead to problems.

[0004] Furthermore, the known systems and devices are generally not flexible or only very flexible. For example, there are devices that are designed for the relatively precise conveying and dosing of powder, but these usually allow a relatively low conveyance rate per unit of time. Although there are also devices or systems for the rapid conveying of larger quantities of powder, these allow a much less precise determination of the conveyance rate or dosing. A further requirement for the devices used for conveying is the ability to design them as a closed system. This is particularly desirable when conveying hazardous substances, for example lithium compounds for battery production. In addition, the devices and devices used for conveying must usually be easy and quick to clean, which places additional demands on their design.

[0005] EP 0 937 004 B2 discloses a device and a method for pneumatically conveying powder. The device has a cylindrical chamber assigned to a collecting container as a dosing chamber, into which chamber powder can be sucked from a powder feed line with the aid of negative pressure, the dosing chamber being supplied with negative pressure through a diaphragm. The stationary diaphragm has the task of preventing powder from being sucked into the negative pressure line. The chamber is not completely filled with powder before emptying during the suction phase. The dosing chamber is emptied into the collecting container by pressurizing the chamber through a separate feed line and in such a way that the powder is conveyed through a lower outlet opening into the collecting container. A weighing system can be assigned to the collecting container so that the quantity of powder conveyed or collected can be recorded.

[0006] EP 0 789 230 A1 discloses a complex dosing device for dosing powder, in which the dosing volume of a dosing chamber can be adjusted by means of an adjustably arranged dosing needle projecting into the chamber. During dosing, a vacuum is applied to a vacuum connection of the dosing chamber in order to suck the powder to be dosed into the chamber via an inlet space. After the filling process, the dosing chamber is emptied by generating an overpressure and opening a closure flap. EP 3184 971 A1 discloses a complex dosing device for micro-quantities, comprising a dosing chamber into which powder can be sucked by means of a vacuum, wherein the dosing chamber has filter means in the form of suction openings formed in a peripheral wall for retaining the powder.The powder is ejected from the dosing chamber using an ejection piston instead of compressed air to minimize the risk of scattering even the smallest amounts of powder.

[0007] DE 102010054649 B3 discloses a powder dosing device with a dosing chamber with a variable volume, wherein the dosing chamber can be subjected to negative pressure through a membrane defining the dosing chamber to draw in powder from a powder supply line. The membrane is adjustable relative to an outlet opening to adjust the powder dosing volume and to empty the dosing chamber.

[0008] For use in dosing processes in battery production, screw conveyors are also known, for example from Coperion K-Tron GmbH.

[0009] The known devices and systems have the disadvantage that they do not provide optimal solutions in terms of their conveying efficiency and accuracy, while at the same time aiming for a simple design.

[0010] Based on the aforementioned prior art, the object of the invention is to provide a structurally simple powder dosing device, particularly for pharmaceutical and / or chemical applications, which enables relatively precise dosing of powder and preferably offers flexible application with regard to the delivery rate per unit of time. Furthermore, the object is to provide a correspondingly improved powder dosing method.

[0011] This object is achieved by a powder dosing device and a powder dosing method according to the independent claims. The dependent claims describe advantageous developments of the present invention.

[0012] In a first aspect, the present invention relates to a powder dosing device for the variable dosing of powder quantities, comprising a dosing chamber with a predefined dosing volume, which is connected on the inlet side to a powder supply line and on the outlet side to a discharge line that can be selectively subjected to negative pressure, wherein the dosing chamber is formed by a line section with an inlet valve, an opposite outlet valve, and an intermediate venting valve, and wherein a control unit of the device for selectively controlling the valves for preferably variable dosing is formed in the line section.

[0013] The dosing device according to the invention represents a simple and effective design compared to known devices, enabling effective, reliable, and precise dosing, as well as easier handling and maintenance of the device. The design of the powder dosing device according to the invention also advantageously enables variable dosing or flow control of the powder in the line section and can thus be used for flexible and application-specific dosing. Furthermore, the device enables reliable conveying of conveyed material, in particular for battery production, for example comprising lithium compounds. In the present case, "capable of being subjected to negative pressure" is understood to mean that the discharge line can be connected to or is connected to a negative pressure source or to a unit for generating a negative pressure or a vacuum.The negative pressure source can be part of the device or a system comprising the device.

[0014] In this context, "variable dosing" means that the amount of powder delivered by the dosing chamber per unit of time is adjustable. In particular, at least two, more preferably at least three different operating modes should be adjustable, with which the valves are controlled or operated, and which advantageously differ in the amount of powder delivered per unit of time.

[0015] In a preferred embodiment, the dosing chamber has a fixed dosing volume, which is limited only by the inlet valve, the outlet valve, and the vent valve in an otherwise continuously closed line section. This means that the dosing chamber or line section preferably has no further inlet and / or outlet lines apart from the aforementioned valves.

[0016] Further preferably, the dosing chamber is free of any movable and / or rigidly arranged elements, in particular free of a powder-retaining membrane. This enables an optimized design of the dosing chamber, providing, on the one hand, the simplest possible structure and, on the other hand, a precise dosing volume of the dosing chamber.

[0017] The venting valve is preferably designed to connect the dosing chamber to the ambient air and thus provide an air inlet for the dosing chamber. In a preferred embodiment, the venting valve is connected only to an air filter on the inlet side. This means that the venting valve has no further connections, in particular no compressed air connections. Furthermore, the venting valve or the associated air inlet and / or air filter is advantageously free of an associated, powder-retaining membrane. A membrane arranged in or encompassed by the air filter is advantageously designed only for coarse filtering of the air conveyed through it.

[0018] The line section preferably has a cross-sectional shape and / or cross-sectional area that corresponds to the downstream discharge line and more preferably to the upstream supply line. In particular, preferably no significant cross-sectional jumps are formed between the line section and the upstream supply line and / or the downstream discharge line. This enables a particularly optimized conveyance of the powder through the dosing chamber. In a preferred embodiment, the line section is designed as a pipe section extending along a longitudinal axis with a preferably round cross-sectional profile, wherein the inlet valve and the outlet valve are arranged at two opposite ends.

[0019] In a further preferred embodiment, the line section comprises a T-shaped element, preferably arranged centrally in the metering chamber, by means of which the venting valve is connected to the inlet and outlet valves. The T-shaped element preferably connects three line elements with a preferably substantially uniform cross-sectional shape and / or surface.

[0020] In a preferred embodiment, the device comprises a collection container, which is connected to or connected to the device's discharge line. The collection container preferably comprises a weighing system connected to or integrated with it, or a scale associated with it, for determining the amount of powder stored or received therein. The device is preferably designed to continuously monitor the feed rate into the collection container and, once a predefined amount in the collection container has been reached, to stop the feed rate by means of the dosing chamber.

[0021] The device preferably further comprises a powder container which is connected to the powder feed line, in particular via a hopper, and which contains a larger quantity of powder to be conveyed. Powder can flow from the container into the hopper under the influence of gravity and from there into the powder feed line. The hopper and the powder container can also be designed integrally. The hopper and powder container are advantageously designed to provide a larger quantity of powder to be conveyed. The hopper and / or powder container is preferably designed to be closed or closable. Furthermore, it preferably comprises a weighing system connected to or integrated therewith for determining the weight, in particular in the form of one or more load cells. This makes it possible to determine the quantity of powder conveyed by detecting a loss in weight at the hopper and / or powder container.The device is preferably designed to continuously monitor the quantity of powder to be conveyed contained in the hopper and / or in the container and to stop the conveying once a predefined conveying quantity has been reached.

[0022] The inlet valve and the outlet valve are preferably designed as variably controllable pinch valves. The respective valve can be selectively switched at least into an open position and a closed position. The venting valve is preferably designed as a shut-off valve that can be switched at least between an open and a closed state and preferably as a variably opening valve. In a preferred embodiment, the control unit is designed to variably control the valves of the dosing chamber for dosing at different dosing speeds or for dosing different conveyed powder quantities per unit of time. The control unit is preferably designed to operate the valves for conveying a different dosing quantity in a predetermined time in at least two, preferably at least three different conveying modes.The conveying modes preferably comprise at least one coarse conveying mode and one fine conveying mode. Further advantageously, the conveying modes comprise a medium-fine conveying mode.

[0023] The control unit can be designed to operate the valves in a first coarse conveying mode, in which the inlet valve and the outlet valve are held in a preferably fully open position when negative pressure is applied to the discharge line, and wherein the venting valve is repeatedly opened and closed at predefined intervals to convey powder from the powder supply line to the powder discharge line. By appropriately controlled opening and closing of the venting valve, the conveyed mass flow in the coarse dosing mode can be controlled. In the coarse conveying mode, a high conveying speed is advantageously achieved, for example in order to convey a maximum amount of powder within a predefined time frame. For example, in cooperation with a collecting container assigned to the device, the container can be filled quickly initially.

[0024] The control unit can further be designed to operate the valves in a second medium-fine conveying mode, in which the outlet valve is held in an open position when negative pressure is applied to the discharge line, the venting valve is repeatedly opened and at least partially closed at predefined intervals to convey powder from the powder feed line to the powder discharge line, and optionally the inlet valve is closed and opened again at predefined intervals to limit the amount of powder conveyed. The inlet valve can be used by opening and closing to control the mass flow based on the corresponding opening and / or closing time. The opening duration is preferably between 1 and 5 seconds. The closing time is preferably between 3 and 10 seconds. In addition, the venting valve can be used to control the conveyed mass flow.This also achieves a relatively high conveying speed, whereby a selective limitation of the conveying quantity and thus the conveying speed can be provided. For example, in conjunction with a collecting container assigned to the device, after an initially rapid filling using the coarse conveying mode, a more moderate filling can be provided by the medium-fine conveying mode, particularly towards the end of a filling process of the collecting container. This enables a filling process that is significantly more controlled with regard to the conveying quantity. For example, a weighing system or an associated scale assigned to the collecting container and / or hopper can monitor the amount of powder collected in the collecting container and / or the amount of powder flowing out of the hopper much more precisely.

[0025] The control unit can further be designed to operate the valves in a third fine delivery mode, in which the inlet and outlet valves are opened and closed sequentially when a negative pressure is applied to the outlet line in order to deliver exactly one dosing volume to the dosing chamber during a respective dosing process. This enables particularly precise dosing of the powder. This is particularly advantageous for applications in the pharmaceutical and / or chemical context, where only slight or no deviations are permitted. In this case, the control unit preferably controls the components of the device in such a way that a negative pressure is initially generated in the dosing chamber. For this purpose, the inlet valve and the venting valve are closed, the outlet valve is opened, and negative pressure is generated in the outlet line by means of the vacuum generation unit. The negative pressure is advantageously generated for a period of 1 to 5 seconds.

[0026] The outlet valve is then also closed, creating a sustained negative pressure or vacuum in the closed dosing chamber. This closure is preferably for a period of 1 to 2 seconds.

[0027] In a further step, the inlet valve of the dosing chamber is opened, so that the prevailing negative pressure draws in a sufficient amount of powder to fill the dosing chamber. The outlet valve and the vent valve remain closed. This occurs for a period of preferably 1 to 3 seconds.

[0028] Subsequently, the inlet valve, and thus the dosing chamber containing the powder, is closed again, and the outlet valve and vent valve are opened, allowing the powder contained in the dosing chamber to be transported through the vacuum-operated discharge line. This occurs for a period of preferably 2 to 10 seconds.

[0029] The described sequence can be repeated several times in order to convey a precise amount of powder by means of the dosing chamber of the device, for example to a collection container connected to the device. By means of an associated weighing system on the collection container and / or on the hopper, the conveyed or collected amount of powder can be continuously recorded and monitored. In a preferred embodiment, the control device can be designed to provide different vacuum levels in the dosing chamber. Thus, by briefly controlling the corresponding vacuum generating means or a vacuum generating system, the control device can generate a less strong vacuum or a lower negative pressure. By controlling the vacuum generating means for a correspondingly longer period, a stronger vacuum or a greater negative pressure can be generated.Alternatively, the vacuum level can be adjusted by setting a vacuum in a collection container connected to the discharge line and / or a pre-chamber connected upstream of it. Alternatively, the vacuum level can also be adjusted by adjusting the re-suction phase for vacuum creation in the collection container and / or a pre-chamber associated with it. This eliminates the need for a vacuum level control unit in the collection container.

[0030] Furthermore, in conjunction with a collection container assigned to the device, after an initial rapid filling using the coarse conveying mode and / or the medium-fine conveying mode, a precise conveying process can take place towards the end of a filling process of the collection container, in particular to more accurately achieve a predefined total quantity in the collection container. This enables a highly precise filling process of the collection container with regard to the conveyed quantity. For example, a weighing system or scale assigned to the collection container and / or hopper can precisely monitor the amount of powder collected in the collection container and / or the amount of powder discharged into the hopper.In a further aspect, the invention relates to a system comprising a powder dosing device as described above and a collection container connected thereto, preferably with a connected weighing system, wherein the collection container has a vacuum generation unit connected thereto, which is designed to selectively create negative pressure in the collection container or a region of the collection container, as well as the connected discharge line of the powder dosing device. As a result, negative pressure can be selectively created in the discharge line of the device by means of the vacuum generation unit, which enables the powder to be conveyed to the collection container as described above. The system preferably additionally comprises a hopper and / or powder container connected to the supply line.This is preferably designed to be closed or closable and further comprises a weighing system connected thereto for determining the weight, in particular in the form of one or more load cells.

[0031] In a further aspect, the invention relates to a powder dosing method, in particular for operating a powder dosing device and / or a system as described above, wherein powder is sucked from a supply line by means of negative pressure into a dosing chamber designed as a line section, comprising an inlet valve, an opposite outlet valve, and an intermediate venting valve, and is conveyed by means of negative pressure through a discharge line connected to the dosing chamber by means of selective control of the valves in at least two different conveying modes, preferably comprising at least one coarse conveying mode and one fine conveying mode.

[0032] In a preferred embodiment, the method comprises the step of controlling the valves in a coarse conveying mode, as already described above with reference to the device. A control unit associated with the valves can, for example, control them in such a way that the venting valve, for providing a quantity of powder or a powder plug in the dosing chamber, is closed for a predefined first period of time t1, preferably 2 seconds, when negative pressure is applied to the discharge line, and then opened for a predefined second, shorter period of time t2, preferably 1 second.

[0033] In a preferred embodiment, the method comprises the step of controlling the valves in a medium-fine conveying mode, as already described above with reference to the device. In this case, control can be carried out essentially analogously to the coarse conveying mode, but additionally, the inlet valve is closed and reopened at predefined intervals to limit the amount of powder conveyed.

[0034] In a further preferred embodiment, the method comprises the step of controlling the valves in the fine feed mode, as already described above with reference to the device. Particularly advantageously, the control is carried out in such a way that first, a negative pressure is generated in the closed dosing chamber, then the inlet valve is opened while keeping the outlet valve and the venting valve closed to admit powder into the dosing chamber, and then closed again. Subsequently, the outlet valve and the venting valve are opened again while keeping the inlet valve closed.

[0035] In a preferred embodiment, the method comprises the previously described control by means of coarse, medium-fine and fine conveying modes, such that initially the powder quantity is conveyed, preferably into a collecting container connected to the device, in a coarse conveying mode, and when a predefined target powder quantity is approached the powder quantity is conveyed in the medium-fine and / or fine conveying mode.

[0036] To avoid repetition, the features and advantages described above for the device according to the invention are intended to be disclosed and claimable as features and advantages also applicable to the method according to the invention and vice versa.

[0037] Details, further advantageous effects and details of the present invention are explained below with reference to the purely schematic, merely exemplary drawings.

[0038] Showing:

[0039] Fig.1a, b : a preferred embodiment of an inventive

[0040] Dosing device in side view and partially sectioned side view;

[0041] Fig. 2a-c: a schematic view of the device and system according to the invention in different conveying states; and

[0042] Fig. 3: a schematic diagram of a cumulative amount of powder conveyed with the device and the system according to the invention over time.

[0043] With reference to Figs. 1a and 1b, a preferred embodiment of the powder dosing device 10 according to the invention is described below. The dosing device comprises a dosing chamber 1 with predefined dosing volumes. A powder feed line 2 is arranged on the inlet side of the dosing chamber 1 and is connected to a powder supply (arrow A), in particular a powder container or the like (not shown). A hopper 3 can be provided, which connects the powder supply to the feed line 2. Powder can be conveyed by gravity into the hopper 3 and the feed line 2 connected thereto.

[0044] On the output side, the dosing chamber is connected to a discharge line 4, which can be selectively subjected to negative pressure in such a way that powder can be conveyed out of the dosing chamber in the discharge line (see arrow B in Fig. 1a).

[0045] The dosing chamber 1 comprises a predefined, unchangeable dosing volume and is formed by a line section with an inlet valve 6, an opposite outlet valve 7, and an intermediate venting valve 8. The line section 5 comprises a linear line section extending along a longitudinal direction L, which is arranged between the supply line and the discharge line 2, 4. Advantageously, a cross-sectional profile of the line section is designed analogously to the connected supply line 2 and discharge line 4. In particular, the line section comprises an inner tube section for powder conveyance, which preferably has a substantially identical cross-sectional shape and size as the connected supply line 2 and discharge line 4. The line section 5 is designed to be selectively separable from the supply line 2 and the discharge line 4 by means of opposing valves 6, 7.The valves 6,7 are advantageously designed as variably controllable pinch valves.

[0046] The dosing volume is advantageously limited only by the aforementioned valves 7, 8, 9 and the inner wall of the line section and, in particular, has no additional supply and / or discharge lines. Furthermore, the dosing chamber 1 or the dosing volume of the dosing chamber is advantageously free of any movable and / or rigidly arranged elements, in particular, free of a powder-retaining membrane.

[0047] The vent valve 8 is preferably arranged in a lateral surface of the line section. In this case, the vent valve 8 can be arranged in a preferably linear line section, which is connected to the axial line section by means of a T-connection or by means of a T-shaped element. The vent valve 8 is advantageously designed as a shut-off valve that can be switched at least between an open and a closed state and more preferably as a variably opening shut-off valve. As a result, the conveyed mass flow can be controlled by appropriately opening or closing the vent valve 8. An air filter 9 is provided on the inlet side of the vent valve 8. This preferably serves solely to filter the ambient air that is sucked into the vent valve.

[0048] The device 10 further comprises a control unit 41 (cf. Fig. 2a-c), which is designed to control the valves 7, 8, 9 of the dosing chamber 1 in a variably timed manner for dosing at different dosing speeds. In this case, the control unit 41 is particularly designed to control the valves in different operating modes, which preferably differ in the respective amount of powder conveyed per unit of time. The control unit 41 can in particular have a position controller 20 connected to the valves 7, 8, 9.

[0049] The control unit 41 is preferably designed to operate the valves 6, 7, 8 in a first coarse conveying mode, in which the inlet valve 6 and the outlet valve 7 are held in a preferably fully open position when a negative pressure is applied to the discharge line 4. As a result, powder is continuously conveyed from the powder feed line 2 and a powder container connected thereto through the metering chamber 1 into the discharge line 4 and, for example, into a collection container 30 connected thereto (see Fig. 2a). The venting valve 8 is repeatedly opened and closed at predefined time intervals in order to build up sufficient negative pressure in the chamber and to promote the continuous and rapid conveyance of individual powder plugs through the metering chamber into the discharge line 4.In a preferred embodiment, the venting valve 8 can be completely closed, for example, for 2 seconds to transport a predefined amount from the supply line 2 into the dosing chamber 1, thereby forming a powder plug, and then opened for, for example, 1 second to convey the powder plug through the discharge line 4. This control can be carried out, for example, for 9 seconds, so that the device forms and conveys 3 powder plugs, each lasting 2 seconds, for example, in the predetermined time of 9 seconds.

[0050] The control unit is further advantageously configured to operate the valves 6, 7, 8 in a second medium-fine conveying mode, in which the outlet valve 7 is held in an open position when negative pressure is applied to the discharge line 4, the venting valve 8 is repeatedly opened and at least partially closed at predefined intervals to convey powder from the powder feed line 2 into the powder discharge line 4, and optionally the inlet valve 6 is closed and reopened at predefined intervals to limit the amount of powder conveyed. For example, the venting valve can be opened to less than 100%, for example, only 50%, while the inlet valve 6 can be continuously switched between an open and a closed position.In a preferred embodiment, the venting valve 8 can be completely closed, for example, for 1 second to transport a predefined amount from the supply line 2 into the dosing chamber 1, thereby forming a powder plug, and then completely opened, for example, for 1 second to convey the powder plug through the discharge line 4. This control can be carried out for 20 seconds, for example, so that the device forms and conveys 10 powder plugs of 1 second each in the specified time of 20 seconds.

[0051] The control unit is further advantageously configured to operate the valves 6, 7, 8 in a third fine delivery mode, in which the inlet and outlet valves 6, 7 are opened and closed sequentially when a negative pressure is applied to the discharge line 4, in order to deliver precisely one dosing volume of the dosing chamber 1 and thus a very precise amount of powder during a dosing process. The corresponding control of the valves in the fine delivery mode is described below as an example in connection with Fig. 2a-c.

[0052] Fig. 2a-c show the system 40 according to the invention comprising the device 10 and a collecting container 30 connected thereto, which is connected to the discharge line 4 of the device 10 and is designed to receive the amount of powder conveyed by means of the device 10.

[0053] In addition to the collection container 30, the system 40 comprises a weighing system 33 connected thereto for determining the weight of the amount of powder collected in the container 30. The weighing system 33 is preferably connected to the control unit 30 of the device 10, so that the valves 7, 8, 9 can be selectively controlled depending on a detected amount of powder in the container 30. The system 30 further comprises a vacuum generation unit 31 which is designed to selectively create negative pressure in the collection container 30 or a region 32 of the collection container, as well as the associated discharge line 4 of the powder dosing device 10. The region 32 can be designed as a pre-chamber of the collection container 30, which can be selectively opened by means of a lower outlet opening 34 such that the powder collected therein can be transferred or conveyed into the collection container 30 by gravity.Alternatively or additionally, the contents of the prechamber 32 can be transferred into the collecting container 30 by introducing excess pressure and simultaneously opening the opening 34. The collecting container can be designed analogously to the device according to EP 0 937 004 B2. For this purpose, the prechamber can have a supply line 35 for compressed air or nitrogen.

[0054] As shown in Fig. 2a, a negative pressure is first generated in the dosing chamber 1. For this purpose, the inlet valve 6 and the vent valve 8 are closed, the outlet valve 7 is opened, and negative pressure is generated in the discharge line 4 by means of the vacuum generation unit 31. The vacuum generation unit 31 can simultaneously generate negative pressure in the pre-chamber 32, with an intermediate valve 36 arranged between the pre-chamber 32 and the discharge line 4 being open.

[0055] Subsequently, as shown in Fig. 2b, the outlet valve 7 and preferably the intermediate valve 36 are also closed, thereby maintaining a sustained negative pressure or vacuum in the closed dosing chamber 1. Another intermediate valve 37, by means of which the vacuum generation unit 31 is connected to the pre-chamber 32, can also be closed. At the same time or subsequently, the inlet valve 6 of the dosing chamber 1 is opened, so that the prevailing negative pressure draws in a quantity of powder sufficient to fill the dosing chamber. Subsequently, the inlet valve 6, and thus the dosing chamber 1 with the dosing volume filled with powder, is closed again.

[0056] As shown in Fig. 2c, the outlet valve 7 and the vent valve 8 are then opened while the inlet valve 6 is closed, so that the negative pressure prevailing in the outlet line 4 conveys the powder to the collection container 30. At the same time, the intermediate valve 36 between the outlet line 4 and the pre-chamber 32 is opened. This can be repeated several times to convey a precise amount of powder to the collection container 30 by means of the dosing chamber 1 of the device 10. The weighing system 33 can continuously record and monitor the amount of powder 38 conveyed or collected in the collection container 30.

[0057] The powder collected in the pre-chamber 32 can be conveyed into the collection container 30 at predefined intervals by means of the outlet opening 34 and advantageously with the introduction of compressed air through a supply line 35 which connects the chamber 32, for example, to a high-pressure generation system 35a or a low-pressure generation system 35b.

[0058] Fig. 3 shows a schematic representation of the powder quantity 38 collected in the collection container 30 over a predefined period of time t. As shown in the graph 39, for the most accurate and, at the same time, the fastest possible filling, the device 10 is now controlled by the control unit 41 such that the powder quantity is initially conveyed into the collection container 30 in a coarse conveying mode (graph section 39a). This allows the fastest possible conveying with sufficient accuracy to be achieved. The collected conveyed quantity is continuously recorded via the weighing system 33 and / or via the weight detection means 42 assigned to the hopper 3, for example in the form of load cells. When a predefined target powder quantity or target conveyed quantity MT is approached, the device 10 is operated in a medium-fine conveying mode (graph section 39b), as described above.In this case, a significantly smaller amount of powder is conveyed per unit of time. As the predefined target powder quantity or target delivery rate MT is further approached, the device 10 is controlled in a final step such that delivery occurs in fine delivery mode (graph section 39c). This results in very precise dosing of the delivery rate into the collection container, enabling the target delivery rate in the collection container 30 to be achieved very precisely.

[0059] List of reference symbols

[0060] 1 dosing chamber

[0061] 2 powder feed line

[0062] 3 hoppers / containers

[0063] 4 Derivation

[0064] 5 line section

[0065] 6 Inlet valve

[0066] 7 Exhaust valve

[0067] 8 Ventilation valve

[0068] 9 air filters

[0069] 10 Powder dosing device

[0070] 20 positioners

[0071] 30 collection containers

[0072] 31 Vacuum generation system

[0073] 32 Antechamber

[0074] 33 Weighing system

[0075] 34 Outlet

[0076] 35 supply line

[0077] 35a, b High pressure / low pressure line

[0078] 36 Intermediate valve derivation

[0079] 37 Intermediate valve vacuum

[0080] 38 Powder quantity collection container

[0081] 39 Flow rate graph

[0082] 39a Coarse conveying mode

[0083] 39b Medium-fine conveying mode

[0084] 39c Fine feed mode

[0085] 40 systems

[0086] 41 Control unit

[0087] 42 Weighing system on the hopper / container

[0088] A,B arrow conveying direction

[0089] L Longitudinal direction t Time

[0090] MT target powder quantity

Claims

Patent claims 1. Powder dosing device (10) for the variable dosing of powder quantities, comprising a dosing chamber (1) with a predefined dosing volume, which is connected on the inlet side to a powder feed line (2) and on the outlet side to a discharge line (4) that can be selectively subjected to negative pressure, characterized in that the dosing chamber (1) is formed by a line section (5) with an inlet valve (6), an opposite outlet valve (7), and an intermediate venting valve (8), and in that a control unit (41) of the device (10) is designed for the selective control of the valves (6, 7, 8) for preferably variable dosing in the line section (5).

2. Powder dosing device according to claim 1, characterized in that the dosing chamber (1) has an unchangeable dosing volume which is limited only by the inlet valve (6), the outlet valve (7) and the venting valve (8) in an otherwise continuously closed line section (5) 3. Powder dosing device according to claim 1 or 2, characterized in that the dosing chamber (1) is free of elements arranged therein in a movable and / or rigid manner, in particular free of a powder-retaining membrane.

4. Powder dosing device according to one of the preceding claims, characterized in that the ventilation valve (8) is connected on the inlet side only to an air filter (9) and in particular is free of an associated powder-retaining membrane.

5. Powder dosing device according to one of the preceding claims, characterized in that the line section (5) is designed as a pipe section extending along a longitudinal axis (L) with a preferably round cross-sectional profile, wherein the inlet valve (6) and the outlet valve (7) are arranged at two opposite ends.

6. Powder dosing device according to one of the preceding claims, characterized in that the line section (5) has a T-shaped element, preferably arranged centrally in the dosing chamber, by means of which the venting valve (8) is connected to the inlet and outlet valves (6, 7).

7. Powder dosing device according to one of the preceding claims, characterized in that the inlet valve (6) and the outlet valve (7) are designed as variably controllable pinch valves.

8. Powder dosing device according to one of the preceding claims, characterized in that the ventilation valve (8) is designed as a shut-off valve which can be switched at least between an open and a closed state and preferably as a variably opening shut-off valve.

9. Powder dosing device according to one of the preceding claims, characterized in that the control unit (41) is designed to control the valves (7, 8, 9) of the dosing chamber (1) in a variably timed manner for dosing at different dosing speeds.

10. Powder dosing device according to claim 9, characterized in that the control unit (41) is designed such that the valves can be operated in at least two, preferably at least three different conveying modes for conveying a different dosing quantity in a predetermined time, preferably comprising at least one coarse conveying mode and one fine conveying mode.

11. Powder dosing device according to one of the preceding claims, characterized in that the control unit (41) is designed to operate the valves (6, 7, 8) in a first coarse conveying mode, in which the inlet valve (6) and the outlet valve (7) are held in a preferably fully open position when negative pressure is applied to the discharge line (4), and wherein the venting valve (8) is repeatedly opened and closed at predefined time intervals to convey powder from the powder feed line (2) into the powder discharge line (4).

12. Powder dosing device according to one of the preceding claims, characterized in that the control unit (41) is designed to operate the valves (6, 7, 8) in a second medium-fine conveying mode, in which the outlet valve (7) is held in an open position when negative pressure is applied to the discharge line (4), the venting valve (8) is repeatedly opened and at least partially closed at predefined time intervals to convey powder from the powder feed line (2) into the powder discharge line (4), and optionally the inlet valve (6) is closed and opened again at predefined intervals to limit the amount of powder conveyed.

13. Powder dosing device according to one of the preceding claims, characterized in that the control unit (41) is designed to operate the valves (6, 7, 8) in a third fine conveying mode, in which the inlet and outlet valves (6, 7) are opened and closed sequentially when negative pressure is applied to the discharge line (4) in order to convey exactly one dosing volume of the dosing chamber (1) during a dosing process.

14. Powder dosing device according to one of the preceding claims, characterized in that the discharge line (4) is connected to a preferably closed or closable collecting container (30) with a weighing system (33) connected thereto for determining the weight of the amount of powder stored therein.

15. Powder dosing device according to one of the preceding claims, characterized in that the feed line (2) is connected to a preferably closed or closable hopper (3) for providing a quantity of powder to be conveyed, with a weighing system (42) connected thereto for determining the weight, in particular in the form of one or more load cells.

16. System (40) comprising a powder dosing device (10) according to one of the preceding claims and a collecting container (30) connected thereto, wherein the collecting container (30) has a vacuum generation unit (31) connected thereto, which is designed to selectively form negative pressure in the collecting container (30) or a region (32) of the collecting container, as well as the connected discharge line (4) of the powder dosing device (10).

17. Powder dosing method, in particular for operating a powder dosing device and / or the system according to one of the preceding claims, wherein powder is sucked from a feed line (2) with the aid of negative pressure into a dosing chamber (1) designed as a line section (5), comprising an inlet valve (6), an opposite outlet valve (7), and an intermediate venting valve (8), and is conveyed from the dosing chamber (1) by means of selective control of the valves (6, 7, 8) in at least two different conveying modes, preferably comprising at least one coarse conveying mode and one fine conveying mode, through a discharge line (4) connected to the dosing chamber (1) by means of negative pressure.

18. Powder dosing method according to claim 17, wherein in a first coarse conveying mode, a control unit (41) assigned to the valves (6, 7, 8) controls them in such a way that the venting valve (8) for providing a powder plug in the dosing chamber (1) when negative pressure is applied to the discharge line (4) is closed for a predefined first time period t1 of preferably 2 seconds and then opened for a predefined second, shorter time period t2 of preferably 1 second.

19. Powder dosing method according to claim 18, wherein additionally the inlet valve (6) is closed and reopened at predefined intervals to limit the amount of powder conveyed.

20. Powder dosing method according to one of claims 17 to 19, wherein in a fine conveying mode a control unit (41) assigned to the valves (6, 7, 8) controls them in such a way that firstly a negative pressure is generated in the closed dosing chamber (1), then the inlet valve (6) is closed while keeping the Outlet valve (7) and ventilation valve (8) are opened to admit powder into the dosing chamber (1) and then closed again, and then the outlet valve (7) and ventilation valve (8) are opened again while keeping the inlet valve (6) closed.

21. Powder dosing method according to one of claims 17 to 20, wherein the control unit (41) controls the valves (6, 7, 8) in such a way that initially a conveying of the powder quantity, preferably into a collecting container (30) connected to the device (10), takes place in a coarse conveying mode, and when approaching a predefined target powder quantity, a conveying of the powder quantity takes place in the fine conveying mode.

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