WO2023042114A1

WO2023042114A1 - Measuring device for measuring the mass flow of a powder

Info

Publication number: WO2023042114A1
Application number: PCT/IB2022/058705
Authority: WO
Inventors: Louis Greet J. VERHEYEN
Original assignee: Vx Management Bv
Priority date: 2021-09-17
Filing date: 2022-09-15
Publication date: 2023-03-23

Abstract

Measuring device.for measuring the mass flow of powders, whereby it is a throughput device (1) that contains a housing (3) with an entry (25) at the top and an exit (6) at. the bottom, whereby the entry (25) ends centrally in the housing (3) and whereby the housing (3) contains a distribution wheel (7) that is coaxially mounted in the h o u s i n g (3) rotatably around a vertical shaft and. that is provided with an inlet (10) around the entry (25) and an outlet (11) at a contour of the distribution wheel (9), whereby a drive (12) is provided for the distribution wheel (7) at a set speed of rotation (13), and whereby the housing (3) further contains a turbine wheel (14) that is mounted rotatably coaxially around the distribution wheel (7) for collecting the powder from the distribution wheel (7) with an inlet (17) opposite the outlet (11) of the distribution wheel (7) and an outlet (18), whereby means are provided (15) to determine at least one operating parameter (21,23,24) of the turbine wheel (14) and convert it into a measuring signal which is a measure for the mass flow.

Description

Measuring device for measuring the mass flow of a powder

The present invention relates ttoo a measuring device for continuously measuring mass flows of powders.

Continuous is understood to mean that continuous measurements are possible, which does not exclude that the device can also be used to measure at discrete times.

Various mechanical and non-mechanical systems are known for continuously measuring mass flows.

Non-mechanical systems are intended more for measuring mass flows of gases and liquids but are usually not adapted and not accurate enough for powders.

Known mechanical systems that do come into consideration for measuring powder flows are usually based on the Coreolis effect or based on centripetal forces or based on impact forces.

Said mechanical systems lose their accuracy for smaller mass flows because the powder mass present becomes gradually too small compared to the provisions present.

Known mechanical systems which work based on impact forces depart from gravity such that the measurement result is very dependent on all kinds of environmental factors such that the application thereof is also limited to bigger mass flows.

The purpose of the present invention is to offer a solution for measuring mass flows of powders whereby a high accuracy is required and also for mass flows that fall outside the range of the aforementioned known measurement systems, for example for use with powders in the pharmaceutical industry.

To this end, the invention relates to a measuring device for measuring the mass flow of powders, characterised in that it is a throughput device that contains a housing with an entry at the top for the powder flow to be measured and an exit at the bottom for the measured powder, whereby the entry ends centrally in the housing and whereby the housing contains a distribution wheel that is coaxially mounted in the housing rotatably around a vertical shaft and that is provided with an inlet around the central entry and an outlet at the outer contour of the distribution wheel, whereby the measuring device is provided with a drive for driving the distribution wheel at a set speed of rotation, and whereby the housing further contains a turbine wheel that is mounted coaxially around the distribution wheel for collecting the powder from the distribution wheel with an inlet opposite the outlet of the distribution wheel and an outlet, whereby means are provided to determine at least one operating parameter of the turbine wheel and convert it into a measuring signal that is a measure for the mass flow.

The invention is based on the following principle.

The turbine wheel is powered by the air flow coming from the distribution wheel, mixed with powder coming from the supply pipe according to the formula F= Q*v whereby F is the force which drives the turbine wheel, Q is the mass flow and v is the peripheral velocity of the distribution wheel. According to the aforementioned formula the mass flow Q of the powder-air mixture is proportional to the driving force F of the turbine wheel provided that the peripheral velocity v of the distribution wheel is constant.

Consequently, there are different possibilities to generate a measuring signal by means of the turbine wheel that is proportional to the mass flow.

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

A second possibility is to stop the turbine wheel by means of a so-called weak spring which allows an angular rotation that is proportional to the mass flow.

A third possibility is to let the turbine wheel rotate freely whereby the speed of rotation increases until a balance is achieved between the driving force F and the frictional force on the turbine wheel such that the speed of rotation of the turbine wheel is a measure for the mass flow.

The advantage of letting the turbine wheel rotate freely is that the set up and regulation are relatively simple and cheap and moreover that the impact of the powder against the turbine is minimal which is favourable for impact-sensitive powders and decreases the risk of wear and tear.

Preferably, the turbine wheel is formed such that it can receive the kinetic energy of the powder coming from the distribution wheel maximally and convert said energy into a torque or a speed of rotation without the turbine wheel being hindered by the passing powder.

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

The measuring device according to this embodiment offers the following advantages compared to the known measurement systems.

All the passing powder is homogenously distributed by the distribution wheel over its contour and flung against the turbine wheel at a clearly defined speed such that said turbine wheel, regardless of the gravity, receives aa measureable torque, angular rotation or speed proportional to the mass of the passing powder.

Another characteristic of said measuring device is that through the operation of the distribution wheel, the present horizontal parts where powder accumulation could occur are self-cleaning.

Further, the powder does not come into contact with horizontal surfaces such that after use very little powder remains in the device such that the device is simple to clean and is suitable for "CIP" and/or "WIP" cleaning.

The measuring system is relatively insensitive for interference from the surroundings such that no special provisions are necessary for mounting. The measuring device can be adjusted with external scales to calibrate the measuring signal.

With the intention of better showing the characteristics of the invention, aa few preferred embodiments of a measuring device according to the invention are described hereinafter by way of an example, without any limiting nature, with reference to the accompanying drawings, wherein:

Figure 1 A shows a 3D view of the measuring device according to the invention;

Figure 1B shows an exploded view of the internal components of the measuring device of figure 1A;

Figure 2A shows a central vertical cross-section according to line IIA-IIA in figure 1; Figure 2B shows the section indicated in figure 2A by frame F2B on a larger scale;

Figure 3 schematically shows a cross-section according to line III-III in figure 2B but for an embodiment variant with a locked turbine wheel;

Figure 4 schematically shows another embodiment variant whereby the turbine wheel is stopped by means of a weak spring;

Figure 5 shows yet another preferred embodiment variant with a freely rotating turbine wheel;

Figure 6 shows possible embodiments of the distribution wheel;

Figure 7 shows possible embodiments of the turbine wheel; Figure 8 shows a vertical cross-section of yet another embodiment variant whereby the turbine wheel is concealed in the distribution wheel. The embodiment of a measuring device 1 according to the invention shown in figures 1A and 1B is intended for measuring the mass flow of powders.

Said measuring device 1 is a throughput device, with a supply tube 2 at the top which centrally connects to a housing 3 which, in this case, is composed of a dome-shaped lid 4 at the top that connects to a funnel 5 that ends at the bottom in an exit 6 for the discharge of the measured powder.

The end 25 of the supply tube protrudes a certain length through the lid 4 in the housing 3.

Vertically under the level of said end 25 of the supply tube

2 and coaxially with said end 25 of the supply tube 2, a distribution wheel 7 is mounted for collecting the powder that falls on it from the entry (25) under the influence of gravity and that is coaxially rotatable around said end 25 of the supply tube 2, as shown in figures 2A and 2B.

The distribution wheel 7 is provided here with blades 8 which delimit channels 9 with an inlet 10 around the central end 25 of the supply tube 2 for receiving and immediately moving powder aanndd aann outlet 11 at the oouutteerr contour of the distribution wheel 7 along which the powder leaves the distribution wheel 7.

Preferably, the measuring device 1 is provided with one single rotational drive, namely a drive 12 shown in figures 1A and 2A and which gives the distribution wheel 7 a set constant speed of rotation 13 around a vertical geometric axis X-X'. In the example of the figures, the drive 12 is mounted coaxially with the central end 25 of the supply tube 2.

Figures 6A to 6D show embodiments of the distribution wheel 7 with open channels 9 and closed channels 9. In the extreme, an ordinary flat disk without blades (not shown) can also be used to spread the powder.

Further, a turbine wheel 14 is coaxially mounted around the distribution wheel 7 in the dome-shaped lid 4. In this example, the turbine wheel 14 is directly mounted oonn an axially incorporated measuring means 15 but depending on the desired measuring signal and the desired embodiment can also be freely bearing-mounted, coaxially with the distribution wheel 7.

Various embodiments of the turbine wheel 14 are possible as illustrated in figures 7A to 7D. Said embodiments can all function with an associated adapted mounting or bearing.

In the example shown in the figures, the turbine wheel 14 is provided with blades 16 with an inlet 17 opposite the outlet 11 of a distribution wheel 7 and an outlet 18 such that the powder from the distribution wheel 7 collides with the blades 16 of the turbine wheel 14 and is moved in the direction of the outlet 18 of the turbine wheel 14.

In the example shown in figures 3, 4, 5, 7C and 7D, the outlet 18 of the turbine wheel 14 faces downward.

In the embodiment according to figures 1A to 2B, the outlet 18 of the turbine wheel is lateral facing, whereby the powder that leaves the outlet 18 of the turbine wheel 14 collides with the lid 4 and subsequently goes down the funnel 5 such as, for example, with a turbine wheel 14 of the figures 7A and 7B.

Figure 8 shows an embodiment whereby the distribution wheel 7 is expanded with aann outer ring of blades 19, possibly surrounded by a hood, with the aim of discharging the powder that passes the turbine wheel 14 better or in a more targeted way which can be favourable for the measuring accuracy.

In certain cases, a turbine wheel 14 without blades or barely perceptible blades can also be used, in other words a turbine wheel 14 in the form of a flat ring or disk or cone (not shown in the figures). Such turbine wheel 14 without blades can, for example, be advantageous in case of relatively sticky powders or in case of abrasive powders.

At the time that the distribution wheel 7 rotates, a radial air flow is produced in the distribution wheel 7 from the inlet 10 through the channels 9 to the outlet 11 which results in a force on the turbine wheel 14.

Powder that ends up on the distribution wheel 7 through the central end 25 of the supply tube 2 immediately mixes with said air flow and consequently increases the impact force on the turbine wheel 14.

As a result of the constant speed of rotation 13 of the distribution wheel 7 on leaving the distribution wheel 7, said powder-air mixture has a clearly defined tangential speed 20 as shown in figures 3 to 5 with which the powder is flung against or over the turbine wheel 14. The impact on the blades 16 and/or the friction in the case of smooth turbine wheels causes a drive torque on the turbine wheel 14 that determines the mass flow.

Various possibilities for measuring the mass flow exist.

According to a first embodiment as shown in figure 3, the turbine wheel 14 is kept in a locked position whereby the force 21 or the torque needed to hold the turbine wheel 14 in said position is measured, whereby the measuring signal is proportional to the mass flow to be measured and can be suitably converted to a measuring signal for the mass flow.

The measuring means 15 on which the turbine wheel 14 is mounted in figures 2A and 2B, is a torque sensor in this embodiment according to figure 3. Figure 4 shows a second alternative embodiment whereby the turbine wheel 14 is provided with a counter-rotation resistance in the form of a weak spring 22 that is mounted between the turbine wheel 14 and a fixed point of the housing 3.

During use, the impulse of the powder gives the turbine wheel 14 a certain angular rotation 23 against the spring force which is proportional to the collision force of the powder.

Said angular rotation 23 is then measured by the measuring means 15 in an embodiment aass angle sensor and used as a measuring signal for measuring the mass flow. A third and most preferred embodiment is shown in figure 5 whereby in this case the turbine wheel 14 is freely rotatably bearing-mounted in the housing.

Under impulse of the powder, the turbine wheel 14 starts to rotate, it accelerates until the counteracting air friction and the bearing friction and powder friction cause a balance condition, such that the speed of rotation 24 of the turbine wheel 14 proportionally follows the changes in the mass flow.

Air and bearing frictions can be considered as a stable given and the stability thereof is monitored when calibrating the system.

Consequently it can be stated that the speed of rotation 24 of the turbine wheel 14 is proportional to the mass flow according to the aforementioned formula F= Q*v whereby F is the force that drives the turbine wheel, Q is the mass flow and v is the peripheral velocity 20 of the distribution wheel 7.

To measure the speed 24 of the turbine wheel 14, the measuring means 15 can, for example, be a bearing-mounted tachometer or a simple shaft bearing in combination with a hall sensor for the measuring signal.

The thus measured powder that flows from the turbine wheel 14 or in the case of figure 8 from the distribution wheel 7, is collected by a funnel 5 and discharged at the bottom via the exit 6.

It goes without saying that the measuring device 1 allows a continuous measurement of the mass flow flowing through. The measuring signal can be used, for example, to monitor and/or steer the mass flow in a process via a dosing device or the like and, for example, issue aann alarm signal at a set minimum and/or maximum mass flow.

It is noted that the measuring device, aass shown, does not contain a dosing device in the housing which means that all the powder that comes in via the entry 25 flows to the exit 6 without delay such that there is no accumulation on the level of the entry 25 or in the supply tube 2.

It is also noted that the measuring device 1 of the figures does not contain a weighing device for measuring the mass flow per unit of time.

In its simplest form, ffoorr iittss functional operation, the measuring device 1 according to the invention only consists of a housing 3 with an entry 25 and an exit 6 and only the following of the aforementioned components:

• a distribution wheel 7;

• one single drive for tthhee functional operation of the measuring device, namely a drive 12 for the distribution wheel 7;

• a turbine wheel 14; means 15 to determine at least one operating parameter 21,23,24 of the turbine wheel. 14 and convert it into a measuring signal that is a measure for the mass flow.

Only one single drive for the functional operation of the measuring device is understood to mean here that no other rotational drives are needed to be able to use the device as a measuring device, which does not exclude that the device may contain other drives for other functions outside those strictly necessary for measuring the mass flow of the powder.

The present invention is by no means limited to the embodiments described as aann example and shown in the drawings, but a measuring device according to the invention can be realised in all kinds of forms and dimensions, without departing from the scope of the invention.

Claims

Claims.

1.- Measuring device for measuring the mass flow of powders, characterised in that it is a throughput device (1) that contains a housing (3) with an entry (25) at the top for the powder to be measured and an exit (6) at the bottom for the measured powder, whereby the entry (25) ends centrally in the housing (3) and whereby the housing (3) contains a distribution wheel (7) that is coaxially mounted in the housing (3) rotatably around a vertical shaft and that is provided with an inlet (10) around the entry (25) and aann outlet (11) at a contour of the distribution wheel (7), whereby the measuring device (1) is provided with a drive (12) for driving the distribution wheel (7) at a set speed of rotation (13), and whereby the housing (3) further contains a turbine wheel (14) that is mounted rotatably coaxially around the distribution wheel (7) for collecting the powder from the distribution wheel (7) with an inlet (17) opposite the oouuttlleett (11) of the distribution wheel (7)and an outlet (18), whereby means are provided (15) ttoo determine at least oonnee operating parameter (21,23,24) of the turbine wheel (14) and convert it into a measuring signal which is a measure for the mass flow.

2.- Measuring device according to claim 1, characterised in that the turbine wheel (14) is freely rotatably bearing-mounted and that the aforementioned operating parameter is the speed (24) of the turbine wheel (14) which is a measure for the mass flow.

3.- Measuring device according to claim 1, characterised in that the turbine wheel (14) is held in a fixed counter-rotation position and that the operating parameter is the force or the torque (21) that is needed to hold the turbine wheel (14) in said position and is a measure for the mass flow.

4.- Measuring device according to claim 1, characterised in that the turbine wheel (14) is provided with an ascending counter-rotation resistance and that the operating parameter is the angular rotation (23) of the turbine wheel (14) which is a measure for the mass flow.

5.- Dosing device according to claim 4, characterised in that the counter-rotation resistance is obtained by a spring (22) between a point of the turbine wheel (14) and a fixed point of the housing (3).

6.- Measuring device according to any one of the previous claims, characterised in that the distribution wheel (7) is provided with an outer ring of blades (19), possibly surrounded by a hood, to discharge the powder that passed the turbine wheel (14) in a certain direction.

7.- Measuring device according to claim 6, characterised in that the outer ring of blades (19) is surrounded by a hood.

8.- Use of a measuring device according to any one of the previous claims, characterised in that it is used to continuously measure and monitor the mass flow of a powder.

9.- Use according to claim 8, characterised in that the measuring signal of the measuring device is used to control a process .

10.- Use according to claim 9, characterised in that the measuring signal of the measuring device is used to dose a mass flow of the process.