BE1029762B1 - dosing device - Google Patents

Abstract

Dosing device for dosing the mass flow rate of powders, characterized in that it is a flow-through device (1, 51, 52) with a housing (2-49) with an inlet (4) and an outlet (5), the inlet (4 ) contains a dosing valve (6) for the powder which is adjustable by means of a control system (19) and the housing (2) contains a distribution wheel (9) coaxial in the housing (2) rotatable about an axis around the dosing valve (6 ) with an inlet (12) opposite the metering valve (6) and an outlet (13) at the outer periphery, the metering device (1) being provided with a drive (50) for the distribution wheel (9) at a set rotational speed (59) , and wherein the housing (2-49) further includes a turbine wheel (14) rotatable coaxially about the distributor wheel (9) for collecting the powder from the distributor wheel (9), there being means for adjusting at least one operating parameter (54, 55 , 57) of the turbine wheel (14) and the aforementioned control system (19) is provided to keep this operating parameter (54, 55, 57) constant during use by controlling the metering valve (6).

Description

dosing device.

The present invention relates to a dosing set for continuous dosing of powder.

Various systems for continuous dosing of PCeder are known. in the pharmaceutical industry, "loss in weight" dosing systems (LIW) are mainly used because of their accuracy,

These “ioss in weight” devices consist of a vessel that is filled with powder through an entrance and can be closed in a controlled manner by means of Archimedes screws or vibrations or sliding movements or valves or the like at the exit.

The whole is placed on a scale, whereby the decrease of the weighed weight as a function of time is a reflection of the mass flow rate of the PCeder.

However, these LIW doscer devices have several disadvantages,

They are sensitive to vibrations from the environment and must therefore be set up vibration-free for an accurate measurement result,

During the refilling of the barrel, the drop in weight cannot be measured, so that the Archimedes screws temporarily turn without measurement.

Refilling the vessel must therefore be done in a short time and can cause significant ripples in the mass flow rate,

The entrance and exit of the vessel of an LIW device must be connected to the fixed world with flexible bellows to ensure that the feed transport proceeds without scaffolding and at the same time to limit invised from the outside on the measuring and control system as much as possible.

The mounting of these bellows is critical for the proper functioning of the measuring system.

These bellows are also prone to powder build-up which can come off uncontrollably and interfere with the measurement.

All of these irregularities can be problematic so that additional smoothing may be desirable.

In addition, a relatively large amount of powder is also lost, for example from the moment of start-up until the operating state is reached, and powder that remains behind in the many horizontal parts, corners and sides of the mechanism after the process has ended.

To clean the dosing unit, it must be disassembled so that the separate parts can be cleaned separately, which makes the dosing device rather unsuitable for cleaning in place {CIP} or 'wash in place (WIP)' cleaning in situ.

Disassembling and reassembling the dosing cell sets for cleaning and switching to other powders takes time, is labour-intensive and is therefore associated with relatively high costs.

Lose in weight devices therefore give little flexibility to dosing processes and can be problematic when using toxic powders,

The present invention aims to provide a solution to at least one or more of the aforementioned and other disadvantages.

To this end, the invention relates to a dosing device for dosing the mass flow rate of powders, which is characterized in that it is a continuous device comprising a housing with an inlet at the top for the product to be dosed and an outlet at the bottom for the dosed powder, the inlet opening centrally into the housing and a metering valve having an adjustable outflow for the powder that is controllable by means of a control system and wherein the housing includes a distribution wheel mounted coaxially in the housing about an axis about the metering valve and having an inlet opposite the outflow from the metering valve and an outlet at the outer periphery of the metering wheel, the metering unit being provided with a drive for driving the metering wheel at a set rotational speed, and wherein the housing further comprises a turbine wheel rotatably coaxially arranged around the metering wheel for collecting the powder from the distributor wheel with a sensor opposite the outlet of the distributor wheel and an outlet, wherein there are means for determining at least one operating parameter of the turbine wheel and wherein the aforesaid control system is provided to keep this operating parameter constant during use by controlling the outflow of the dosing valve.

Zuik dosing device is easy to realize and gives a continuous and constant powder flow at the outlet.

The invention is based on the following principle.

The Lurbine wheel is = driven by the air stream coming from the distributor wheel, cemenod with powder coming from the metering valve according to the formula F= Q*v where F is the force driving the turbine wheel, Q is the mass flow rate and v is the circumferential speed of the distributor wheel .

According to the above formula, the mass flow © of the powder-air mixture is proportional to the driving force F of the turbine wheel, provided that the peripheral speed v of the distribution wheel is constant,

Consequently, there are various possibilities to generate a measurement signal proportional to the mass flow rate by means of the turbine wheel and then use that measurement signal to adjust the metering valve.

A first possibility is to measure the force or torque with which the turbine wheel can be blocked.

The second possibility is to restrain the turbine wheel by means of a slack spring that allows an angular displacement proportional to the mass flow rate.

A third possibility is to let the turbine wheel rotate freely, whereby the speed increases: Let there be an equilibrium between the driving force F and the frictional force of the turbine wheel, so that the speed of the turbine becomes constant and times 15 for the mass flow rate.

Allowing the turbine wheel to rotate freely has the advantage that the

The construction and control are relatively simple and inexpensive and, in addition, the impact of the powder against the turbine is minimal, which is favorable for impact-sensitive powders.

The turbine wheel is preferably shaped in such a way that it absorbs the kinetic energy of the powder coming from the distribution wheel at a maximum and converts it into a static or a dynamic torque or rotational speed without the turbine wheel being diminished by the passed powder.

The turbine wheel preferably has a low mass inertia and is provided with a bearing or a suspension which has a constant, preferably low friction in order to optimally convert changes in the mass flow rate into changes in the measurement signal of the turbine wheel.

The dosing device according to the output offers the following advantages over the known LIW systems.

The mass flow rate of the dosed powder is very accurate and unlike “isss in weight” and “gain in weight”

Systems continuously under control by controlling the torque or angular rotation or rotational speed of the turbine wheel so that the risk of irregularities that need to be smoothed out is structurally smaller than with loss in weight dossers.

Due to the absence of a scale that continuously measures the weight of the powder present, the device does not require any flexible connections or Daigen so that: it can be properly hermetically sealed so that it can be used for dosing highly toxic substances.

Another characteristic of this dosing device is that due to the operation of the distribution wheel, the horizontal parts present where powder accumulation could occur are self-cleaning.

Furthermore, the powder does not come into contact with horizontal surfaces, so that very little powder remains in the device after use, making the device easy to clean and suitable for "CIP" and/or "WIP" cleaning,

The mect and control system is relatively insensitive to disturbances from the environment, so that no special facilities are required for installation.

In a basic configuration, the metering device can be adjusted with an external scale to determine the desired lake signal and has no monitoring for the stability of the turbine wheel friction drag.

Another feature of the impeller operation is that the powder flow is controlled regardless of the turbine impeller! homogeneously distributed along the circumference of the housing, which makes it possible to split this powder flow at that location in an adjustable manner into at least two powder flows that have the same ratio to each other at any time and of which one powder flow is the desired dosing flow and the other is a residual flow of the excess powder.

The advantage of this split at that location is that the doser valve can always function in an optimal working range, even if the desired mass flow rate to the exit is significantly smaller, so that very small accurate doses are possible.

The diverting valve connects to a funnel with a separate outlet for each stream.

Another advantage is that the residual flow can be used during dosing to control the course of the mass flow rate of the dosing flow,

To this end, a control system is provided in the dosing device to which the residual flow can be diverted for indirect control of possible deviations of the delivered mass flow rate from the next mass flow rate.

The control system is provided to generate an Éout signal which can be used to provide an alarm signal or to feed back to the control system to adjust the turbine wheel control rate.

Preferably, the control system is equipped with a built-in “gain in weight” scale with an open collection pot that rests reversibly on a load cell that generates a curve of increasing weight each time during filling with powder,

When the poll is full, it is reversed and the measured powder can already be fed into a collector to which a return system may be connected.

A system of directional valves allows the dosing flow and the residual flow to be diverted separately or together, as desired, directly to the dosing outlet or to the residual outlet with the "gain in weight" scale or directly to a collector from which the collected feed is returned to the feed via a return system. entrance are led.

The combination of tilt tip gene and built-in gain in the weight scale offers the advantage that the dosing device can adjust itself automatically by first determining the corresponding measurement signal from the turbine wheel after entering the desired mass flow rate and then switching the correct mass flow rate to the output.

For example, the return system is equipped with an Archimedes screw in a vertical tube for the vertical transport of the residual powder from the aforementioned collector at the bottom to the inlet of the dosing device at the top,

Feeding new powder through the collector has the advantage that the return system is the only system responsible for the powder level at the top of the unit inlet.

This return system can preferably be designed as a tube with an Archimedes screw.

A tube with an Archimedes screw has the advantage that it is a very compact system and easy to clean.

When placed centrally in the axis of the device, the Archimedean screw can serve directly as a metering valve, with the end of the screw scattering the lifted powder directly in or over the distribution wheel.

The advantage of placement in the axis is that a separate dosing tip and monitoring of the powder level at the top entrance are no longer necessary, making the design compact.

With the insight to better understand the features of the invention

Wages, some preferred embodiments of a dosing device according to the invention are described below, by way of example without any limiting character, with reference to the accompanying drawings, in which:

Figure 1A provides an SD view of the hasismode! of the dosing device according to the invention;

Figure iB shows the base model of Figure 1A without cover and supply line:

Figure Z shows a central vertical section of this basic mods);

Figure 3 shows an enlargement of the turbine part of Figure 2;

Figure 4 shows an embodiment with blocked turbine mode;

Figure 5 Is an embodiment where the turbine wheel is stopped with a slack spring;

Figure 6 shows the preferred version with a freely rotating turbine wheel:

Figures 7 and 8 show a disassembled combination of dosing wheel, distribution wheel and turbine wheel:

Figure 2 shows possible versions of the distribution wheel:

FLgure LG shows possible versions of the turbine wheel;

Figure 11 shows an embodiment of the distribution valve;

Figure 12 shows the double funnel;

Figures 13 and 14 show the divider valve cp the double right in two different ratio positions;

Figure 15 schematically shows the operation of the distribution valve on the double seeker:

Figure 16 shows the basic model of the dosing device of figure 1 extended with a directional valve system, built-in gain in weight scale and a return system for unused powder, new powder inlet;

Figure 17 shows the circuit of the directional valves of Figure 16 when all the dosed powder is directed to the vitgang;

Figure 18 shows the switching of the tilt-turns during the start-up sequence;

Figure 19 shows the circuit of directional valves during cegraving with the parallel current being fed to the gain in weight scale;

Figure 20 shows an embodiment of the built-in gain in weight scale of the dosing device of Figure 16;

Figure 21 shows a central vertical section of a dosing device according to the invention with a central Archimedes screw as transport and dosing means;

Figure Z2 shows an exploded version of the dosing device of figure Z1,

The basic model of a dosing device 1 according to the invention shown in Figure 1 is intended for dosing the mass flow rate of powders, in particular for obtaining a desired set mass flow rate.

Li

BE2021/5735

This dosing device ! is a lancing device, with a housing 2 composed of a dome-shaped cover 2 at the top, which connects to a funnel 49 which is vertically cylindrical at the top and ends at the bottom in an outlet 5 for the metered powder,

The cover 2 is provided with an entrance 4 connecting to the pin supply line 60 for the supply of the powder to be dosed, which is preferably centrally placed. inlet 4 is also equipped with a dosing valve 6 with adjustable outflow of the powder,

In this case, the metering valve 6 is constructed as a rotatable disc coaxially arranged in the inlet 4 with a central cone facing Dpoven and fan-shaped ribs 7 around the base as shown in Figures 2 to B,

The dosing valve 6 can be provided with a drive 8 for dosing the mass flow rate of powder passed through, in this case by adjusting the speed of the dosing valve 6,

This drive 8 is provided with a control system 19 with which the outflow of the dosing valve can be regulated

In the dome-shaped cover 2, a distribution wheel 9 is costically arranged, which can be rotated around the metering valve 5, as shown in Figures 2 to 7.

The distribution wheel © is here provided with vanes 10 which delimit channels il with an inlet 12 opposite the outflow of the

C BE2021/5735 dosing valve 5 for receiving powder and an outlet 13 at the outer periphery of the distribution wheel 9 along which the goods exit the distribution wheel.

The dosing device 1 is preferably provided with a drive 50, which is shown in figure Z and which supplies the distribution wheel 9 with a set constant rotational speed 593. In the example of the figures, the drive is

S0fixed internally in the housing.

Figure 3 Pays versions of the distribution wheel 9 with open channels il and closed channels 11 , In extremis an ordinary flat disc without blades can also serve to spread the powder,

Furthermore, a turbine wheel 14 is arranged coaxially in the dome-shaped cover 2, which is freely rotatable around the distribution wheel 5 by means of a turbine bearing 48 as shown in figure 3.

Different versions of the turbine wheel 14 and associated adapted bearings à8 are possible as illustrated in figures 10A to 10E,

The turbine bearing 48 of the turbine wheel 14 preferably has a small diameter and can be placed centrally around, for example, the entrance à Dovenaan for turbine wheels according to figures 1G B and 10 D or at the bottom for turbine wheels according to figure 10

A and Figure 1E,

In the example shown in the figures, the turbine wheel 14 is provided with blades 15 with an inlet 16 opposite the outlet 13 of the distribution wheel 9 and an outlet 17, so that the goods from the distribution wheel 3 collide with the blades 15 of the turbine wheel 14 and move in the direction of the exhaust 17 of the turbine wheel 14 is moved.

In the example shown in Figures 7 and 8, the outlet 17 of the turbine wheel 14 is directed downwards. Examples of such turbine wheels 14 with an outlet 17 downwards are shown in Figures 10C and 10D. in the embodiment according to figures 1 to 3 the outlet 17 of the turbine wheel is directed sideways, the powder leaving the outlet 17 of the turbine wheel 14 collides with the lid 2 and then goes down into the funnel 45 as for example with a turbine wheel 14 of Figures 10A and 10B.

In certain cases a turbine wheel 14 without blades can also be used, in other words a turbine wheel 14 in the form of a flat ring or disc not shown in the figures.

Such a turbine blade 14 without blades can be advantageous, for example, in the case of relatively sticky PCs,

At the moment that the distributor wheel 3 rotates, a radial airflow is created in the distributor wheel % from the inlet 12 through the channels 11 to the outlet 13, which entrains the powder leaving the outlet of the metering valve 6 from the moment the metering valve 6 starts. to rotate and thus loosen powder.

As a result of the constant rotation speed 5% of the distribution wheel $ when it leaves the distribution wheel 3, this powder-air mixture has a well-determined longitudinal velocity 53 as shown in Figures 4 to 6, with which the powder is discharged or thrown over the turbine wheel 14.

The impact on the blades 15 and/or the friction creates a driving torque on the turbine wheel 14 which determines the mass flow rate. There are various possibilities for controlling the mass flow rate. According to a first embodiment as shown in figure 4, the turbine wheel is 14 is used in a blocked condition, in which the force 55 or the torque required to block the turbine wheel 14 serves as a signal to control the metering valve 5 to Le.

The force or torque 55 required to hold the turbine wheel 14 in a fixed position and rotation is measured and the measurement signal is fed back to the control system 19 to control the outflow of the metering valve 6 during operation to keep the measured force or torque constant ,

In Figure 5 a second alternative embodiment is shown in which the turbine wheel 14 is provided with a resistance to rotation in the form of a slack spring 56 fitted between the Lurbine wheel 14 and a fixed point of the housing Z-43,

During use, the impulse of the powder will cause the turbine wheel 14 to receive a certain angular displacement 57 against the spring force, which is proportional to the impact force of the powder.

This angular displacement 57 is then measured and used as a measuring signal for controlling the metering valve 6 in order to keep the angular displacement 57 constant during use by regulating the outflow of the metering valve .

A third and most preferred embodiment 15 is shown in figure ©, in which in this case the turbine wheel 14 is freely rotatable in the housing.

Under the impulse of the powder, the turbine wheel Le begins to rotate, just accelerating until the opposing air friction and the

bearing friction in the bearing 48 to ensure a state of equilibrium, in which the tcerenta! 54 of the turbine wheel 14 sen can get a constant value by controlling the metering valve 6.

This rotational speed 54 of the turbine wheel 14 is proportional to the mass flow rate as explained below.

This constant speed 54 of turbine wheel 14 can be influenced by the tangential speed 53 at which the powder

Air-mix leaves the distributor wheel % but it is kept constant because the Loerental 59 of the distributor wheel is kept constant.

This constant speed 54 of turbine wheel 14 is also influenced by the cooperating air friction at increasing speeds and the bearing friction in the bearing 48 of turbine wheel 14.

However, air and bearing frictions can be regarded as stable data over shorter or longer periods and their stability can also be checked in the further course of the process.

This constant rotational speed 54 of turbine wheel 14 is therefore exclusively influenced by the powder mass that is scattered around in the distribution wheel 5 by the dosing valve &.

It can thus be stated that the rotational speed 54 of the turbine wheel 14 is proportional to the mass flow rate controlled by the dosing valve 6 in accordance with the formula F = Q*v, where F is the force driving the turbine wheel, © is the mass flow rate and v is the circumferential speed 53 of the distribution wheel 9,

The rotational speed 54 of the turbine wheel 14 is measured by a velocity sensor 18 shown in Figures 3, 7 and 8,

By means of a control system 19, shown in Figure 2, the dosing valve 6 can ensure that a rotational speed of turbine wheel 14 and thus also the mass flow rate at the outlet 17 of turbine wheel 14 is kept constant by allowing more or less powder to pass through.

The thus metered powder flowing from the turbine wheel 14 is collected by funnel 49 and discharged at the bottom via outlet 5.

The speed of the turbine wheel 14 to be set for obtaining a desired mass flow rate at the output 5 can be decaled experimentally in advance in the following way by means of an external gain in weight scale (not shown) with which the increasing weight as a function of time is measured, This external scale is not necessarily part of the dcsinger.

If this speed 54 is known, the control system 19 can ensure that this speed 54 remains constant by adjusting the speed of dosing valve 6, resulting in the desired constant mass flow rate at output 5.

Subsequently, the external scale 21 is removed or switched off and the dosing device ! selector for dosing,

It is then sufficient to supply and foul powder continuously in order to always have powder present in the inlet 4 between a minimum and maximum level as shown in figure 2.

By then driving the distribution wheel 3 at a constant speed, powder will be supplied to the outlet 5 at a constant mass flow rate.

Although good results can be achieved with this basic version, a self-adjusting version of a dosing device 51 is described below as an extension of the basic model 1, with which the set speed of the turbine is set automatically at start-up without the need for manual actions and/or of a separate scale and without the need to adjust the mass of powder that is required for the basic model to adjust the dosing unit 1 no longer: must be separately disposed of, so that the spreading of dust can be avoided and the dosing device can also be used for dust-tight

Systems and in case of hcog toxic powders,

An example of such a self-adjusting embodiment of a dosing device 51 according to the invention is shown in figure 16, in which the basic embodiment of figure 1 is additionally provided with a built-in gain in weight scale 22, in combination with a directional tilt system with valves 27-28-20,

With this dosing device Si, the desired mass flow rate is entered at start-up, after which the device adjusts to this and the mass flow rate is only fed to the final output 5 when the desired value iz is reached.

As shown in Figure 16, the domed lid 2 with distributor wheel 9 and turhine wheel 14 and metering valve & in this self-adjusting dosing device 51 is placed on top of a double hopper 23 which is provided with a distributor blade 24 shown in Figures 11 to 15 and with which the powder flow that falls down homogeneously distributed along the circumference of the dome-shaped cover 2 when it leaves the turbine wheel 14 can be split into a dosing flowm and a parallel residual flow that have a constant relationship to each other at any time,

The double funnel 23 therefore has an outlet 26 at the bottom for the dosing flow that will go to outlet 5 and an outlet

FOR the parallel power com that can be recovered automatically later on.

The distribution valve 24, as shown in Figures 11 to 15, is rotatable about the central axis and is set manually or via an algorithm in such a way that the metering valve 6 can always function in the optimum part of its operating range by delivering a set mass flow rate to the

Lright exit 26.

This extends the working range of the dosing device 51 downwards so that it can also be used for the accurate dosing of very small mass flow rates,

Figure 13 shows the divider valve ZA in a corresponding position with an approximate 15%-85% ratio, while in Figure 14 the divider valve is rotated to a 50%3-50% ratio position.

Both powder streams depart from a product which is uniformly distributed at the periphery of the turhine wheel 14 and ends up in the hopper 23 by gravity, so that both streams at the outlets 25 and 26 are also metered in a fixed ratio.

As shown in Figures 16 to 19, the outlets 25 and 26 of the double funnel 24 connect to diverter valves 27 and 28,

Directional valve 28 connects to the dosing output 26 and is connected via a Y-piece 33 containing a directional valve 23 to a built-in gain in weight scale 22.

Depending on the positions of the valves 28 and 29 to be set, the dosing flow can be fed directly to the outlet 5 during operation as shown in figures 17 and 13 or alternatively be led to the balance 22 as shown in figure 18 for the determination of the rotational speed of the turbine wheel 14 when adjusted during the co-start procedure as explained above.

Diverter valve 27 connects to the parallel output 25 of the twin funnel and is directly connected via a bridge 34 to the coliector 36 for recovery of the parallel current during the start-up procedure as shown in Figure 18 or via the Y-piece 33 and diverter 29 to the built-in gain in weight scale 22 during operation as shown in [figure 19,

The parsallei current from rectifier 27 can preferably be fed to the built-in gain in weight scale 22 after the co-start procedure as shown in Figure 19 because the graphs generated by this must remain unchanged during operation and can thus detect irregularities related to air drag or the bearing friction of the turbine wheel 14, the speed of which determines the accuracy of the metered mass flow rate.

Turn-tilt 29 also offers the possibility to utilize the full mass flow rate of the dosing device 51 by forwarding both PCer flows during the start-up procedure to the built-in gain in weight scale 22 and then forwarding the full mass flow rate to the final output 5 as shown in figure 17 ,

As shown in more detail in Figure 20, the built-in gain in weight scale 22 essentially consisted of an open catch pole 30 attached to a shaft coupling 61 with pivot point 58 which can be overturned by means of a drive 32 to empty it without interrupting the powder flow.

Due to the action of the hinge point 58, the collection pot 30 can be supported on a load cell 31 which measures the increasing weight (gain in weight) of the powder received as a function of time.

These measurements are compared with the desired situation by the aforementioned control system 12.

During the start-up procedure of figure 18, the collection pot 30 receives via directional valve 28 the dozer flow, which is gradually increased by the dosing valve 6 until when the gain in weight measurements show that the desired mass flow rate has been reached and therefore the control speed 54 of turbine wheel 14 is known. ,

The mass flow rate is controlled after the start-up procedure by keeping the rotational speed of the turbine wheel 14 constant,

From that moment on, deviations in the increasing weight of load cell 31 can indicate changes in the friction of the turbine wheel lé so that the control system 19 can change the control spring rate of the turbine wheel 14 if necessary, or give an error message,

Collector 36 is a Duffer vat at the bottom that collects powder from the built-in gain in weight scale 22, from the bridging 34 and preferably also freshly supplied new powder via channel 35.

A return system 39 is also connected to collector 36, with which the unused powder can be fed back to the supply line 46 at the top via a return system 39 as shown in figure 16,

Preferably, the powder coming from the built-in gain in weight scale 22 and the powder passing from bridge 34 into collector 36 for return, but the feed line 46 should be given priority over the new powder from channel 35,

This priority can be achieved, for example, by making the angle of inclination of the supply 35 of the new powder to the coliector 36 less steep than the angle of inclination followed by the already used powder from the scale 22 or the bridge 34 to the return system 39,

Consequently, new powder can only flow into collector 36 via channel 35 if the powder level has fallen below the outlet of channel 35 in collector 36.

Collector 36 is also provided with a valve 43 at the bottom, which can be used to drain the entire dosing device 51 and which is also functional when using

WID or CIP cleaning.

Return system 39 may consist of a vertical return tube 40 containing a coaxial Archimedean screw 41 which may have a drive 44 at the top and the end 42 of which is located in the coliector 36 at the bottom.

This end 42 of the Archimedean screw 41 can be, for example, an increase in screw diameter to allow vertical transport of powder from the collector 36 .

At the top, the return system 39 ends in the feed line 46, with the powder being poured into the feed line 46 at a position 60 above a sensor 45 that detects the highest permitted powder level 3,

When this level is reached, the feed system 22 stops supplying powder.

There may also be a second level sensor 48 in supply line 46 which detects the lowest permissible posder level 3 and does not give a start signal for the

Supply system 39.

The implementation of return system 3% is not limited to a return tube 40 with Archimedean screw 41, but it can also be implemented as pneumatic transport, bucket elevator or other known transport systems.

Figures 21 and 22 show a more compact embodiment of dosing device 52 according to the invention, in which the return tube 40 with the Archimedean screw di is placed centrally, coaxial with the verdesirad 9, with the Archimedes screw al taking over the function of dosing valve 6 as the powder flowing through the Archimedes screw 41 is transported upwards and the return tube 40 is left at the top at the height of the distribution wheel $.

In that case the supply line 46 with the sensors 45 and 48 and cok input 4 with the separate metering valve & are omitted and the speed of the Archimedes screw 41 is controlled by the control system 15 to arrive at a constant speed 54 of the turbine wheel 9 and thus at same method to achieve a constant mass flow rate at output 5.

The present invention is by no means limited to the embodiments described by way of example and shown in the figures, but a doscert nest according to the invention can be realized in all kinds of shapes and dimensions without departing from the scope of the invention.

Claims (14)

conclusions, Ll. Dosing device for dosing the mass flow rate of powders, characterized in that it is a door\sopping device {1,51i,52} containing a housing (2-49) with an inlet (6) at the top for the powder to be dosed and an outlet (5) at the bottom for the dosed powder, with the inlet (4) opening centrally in the housing (2) and containing a dosing valve (6) with 19 an adjustable outflow for the powder that is adjustable by means of a control system (19) and wherein the housing (2} contains a distribution wheel {3} which is rotatable coaxially in the housing (Z} around an axis around the dosing valve {6) and which is provided with an inlet (12) opposite the outflow of the doser tip (6 ) and an outlet {12} on the outer circumference of the distribution wheel {9}, wherein the dosing device {1} is provided with a drive (50) for driving the distribution wheel {9} at a set rotational speed (59), and wherein the housing (2-49) further contains a turbine wheel (14) rotatably coaxially arranged around the distributor wheel {9} for collecting the powder from the distributor wheel (5) with an inlet (16) opposite the outlet {13} of the distributor wheel (5) and an outlet (17), there being means for commanding at least one operating parameter (54,55, 57) of the turbine wheel (14) and wherein the aforesaid control system {19} is provided to control this operating parameter {( 54,55,57) during use by controlling the outflow of the dosing valve{6}. 2. Dosing device according to claim 1, characterized in that the turbine wheel (14) is mounted for free rotation and that the main operating parameter is the speed {54} of the turbine wheel (14), which is kept constant during use by regulating the outflow of the dosing valve. (6). A dosing device according to claim 1, characterized in that the turbine wheel (14) is held in a fixed position against rotation and the operating parameter is the force or torque {55} required to fix the turbine wheel (14) in this position. which is kept constant during use by regulating the outflow of the dosing valve (63. a." Doscer device according to claim 1, characterized in that the turbine wheel (14) is provided with a resistance to empty rotation and that the operating parameter is the angular displacement 157) of the turbine wheel (14) which is kept constant during use by regulating the outflow of the metering valve ( 6). Dosing device according to claim 4, characterized in that the resistance to rotation is obtained by a spring (56) between the turbine wheel {14} and a fixed point of the housing (2-49). 6. Dosing device according to one of the preceding claims, characterized in that the dosing device {1} is provided with a distribution valve (24; for splitting the dosed powder coming from the turbine wheel {14} OD into two parallel encoder streams, depending on a desired requested dosing current. and a residual flow of the excess powder, and that the housing (2-49) is provided with two outputs {25 and 20}, respectively a doser output {26} for the requested dosing flow and a parallel residual output (25) for the residual current. Jr. Doscert set according to claim &, characterized in that the doser output (26) can be diverted to a control system for determining the correct operating parameter (54,55,57) to achieve the desired mass flow rate. 8. Dosing device according to claim 7, characterized in that the residual output (253) can be led to the control system for indirect monitoring of possible deviations of the delivered mass flow rate from the desired mass flow rate. 9. Dosing device according to claim 8, characterized in that the control system is provided for generating an error signal which can be used to feed back to the control system {19} for adjustment of the operating parameters 44,55, 57} of the turbine wheel (14 ) or to sound an alarm. Dosing device according to any one of claims 7 to 9, characterized in that the control system has a built-in gain in weight scale (22) in the form of an open co-catch pole (30) attached to a shaft coupling {61} with hinge point (58) which can be tilted by means of a drive (32) in order to empty the collection pot {30} without interrupting the powder flow, whereby the collection pot {30} is supported on a load cell (313) which has just increasing weight. (gain in weight ) of the collected powder as a function of time to determine the captured mass flow rate and compare it with the desired mass flow rate. 11, Dosing device according to one of claims 5 to 15, characterized in that it is provided with a return system (39) to send the excess residual flow back to the input (4). A dosing device according to any one of claims 6 to 11, characterized in that the supply of fresh powder is connected to the return system (39). Dosing device according to claim 12, characterized in that the return system (393) is provided with an Archimedean screw (41) for the vertical transport of the residual powder. 14. Dosing device according to claim 13, characterized in that the Archimedes screw (41) also fulfills the function of the above-mentioned dosing valve (6).