EP2806973B1 - Device and method of dosing a liquid - Google Patents

Description

The present application relates to a device and a method for dosing liquids.

A metering device for fluids is from the DE 35 31 241 C2 known. In this case, liquid is forced through a cannula with the aid of a pressure transducer. A pressure sensor measures the pressure of the liquid in the cannula, the measurement result is fed to a control device for controlling the pressure transducer. When trapped air in the liquid but can not close exactly from the pressure curve on the discharged amount of liquid. This is problematic in dosing operations where the exact dosage of small amounts is important. The document EP 0 865 824 A1 shows a device for dosing a liquid and a pressure measurement within a sample space. The document US 2008/015406 A1 shows a syringe with an intermediate pressure sensor.

Thus, it is an object of the invention to provide a device for dosing of liquids, with which even small amounts of liquid can be dosed as accurately as possible. It is likewise an object of the invention to specify a method for dosing liquids as precisely as possible.

These objects are achieved by the subjects of the independent claims, with advantageous developments of the invention being defined in the dependent claims.

There is provided a device for dosing liquids with a liquid container, a discharge device and a pressure measuring device having a cavity and a pressure sensor for detecting a pressure in the cavity. A first tube device is configured to direct liquid from the liquid container through the interior of the first tube device to the cavity and a second tube device to direct liquid from the cavity through the interior of the second tube device to the discharge device. In this case, the device is set up such that all liquid flowing from the liquid container to the discharge device flows through the cavity.

For example, a tube device may include tubing or tubing or a combination of tubing or tubing and may also include valves and complex branches.

The two paths, one to and one from the cavity, have the advantage that the cavity can be flushed by allowing liquid to flow through the cavity from one path and liquid from the cavity through the other path. Thus, neither air bubbles nor other gas bubbles nor dirt accumulate in the cavity. This is especially important in ultra trace applications. Air bubbles have the disadvantage that from the measured pressure difference can not be reliably determined on the amount of discharged liquid. In addition, gas must not be dosed, otherwise the target volume is not maintained. Air and other gases are usually compressible, so that pressure changes initially cause a deformation of the gas bubbles. Holes in tube devices that are not flushed carry the risk of air bubbles accumulating in them. This is particularly critical for metering devices with very high accuracy requirements.

The structure of the device should therefore be as simple as possible, the surfaces through which the liquid flows, be as smooth as possible. There should be no or the smallest possible dead volumes for the liquid. In addition, the structure should be robust, reliable and safe, so that repeatable without correction by users, for example, for days or weeks, can be dosed. Thus, there is an excellent suitability for automation.

The device can also be used to set a period of time in which liquid is conveyed from the liquid container into the tube device. From the multiplication of the time period times the volume drained by the discharge device per time, the total drained volume can be determined. However, this determination is only correct if there are no air bubbles in the tube system. The presence of air bubbles can at least be detected with the device according to the application. If air bubbles were detected during the dosing process, the metered quantity can be destroyed and the dosing process repeated. Thus, ultra-accurate metering operations can be carried out with the device according to the application.

Impurities that can settle in the cavity and reach the dispensed liquid in a later dosing process, cause contamination of the mixture. The device can thus also be used in particular in mixing processes in which ultra-purity is important, and in particular in mixing processes in which ultra-aggressive fluids are used.

The device according to the application can also be referred to as a form of liquid handling monitoring.

In one embodiment, the liquid container is filled with liquid. This means that there is no gas cushion as provided in some prior art devices. A gas cushion is fundamentally compressible and therefore makes it more difficult to control the discharge based on the measured pressure. In addition, a gas cushion increases the risk of gas bubbles entering the liquid.

Gas cushions or separation gaps require mechanical. moving brackets or injectors. This results in high costs, space requirements and contamination sources. Separation gaps are gas bubbles that are located above the liquid to be dispensed.

In another embodiment, the first tube device includes a tube that opens into the cavity. This hose can be flexibly guided by the pressure measuring device and thus be guided directly into the cavity as simply as possible. This simplifies the assembly of the device.

Particularly suitable is the device when the discharge device has a downwardly open tip with an opening cross-section of less than 0.4 mmm. In such a venting device, the small orifice cross-section provides a high resistance to the liquid so that the pressure in the tube device becomes relatively high even at low dosing speed, and provides a small interface between the liquid and the air at the vent, which improves the accuracy of dosing elevated. The pressure difference between the state in which the device is at rest, and a state in which the device discharges liquid is thus relatively high, with which high-precision monitoring and measurements are possible.

If the draining device has no moving parts, the number of components in the device is reduced because each additional component contains other materials that could cause soiling. For complex systems, the space requirement would be enormous, they would then not be feasible with reasonable effort.

According to one embodiment, a switch is provided between the tube device and the pressure measuring device, by means of which the paths are spatially separated from one another be separated. This switch allows for easy separation between the paths so that they can easily be connected to the different ports of the switch to allow flushing of the cavity.

Preferably, the pressure sensor includes a piezoelectric element. With such a pressure changes can be easily converted into electrical signals.

If the detected signals are interpreted electronically in an evaluation unit and error messages are output according to the signal curves, it is possible to output warnings and to send them to an operator without having to constantly observe the signal progressions.

The evaluation preferably takes place with the aid of a Fourier transformation. With such a complex signal waveforms can be interpreted quickly, so that a quick error message is possible. This allows an operator to intervene immediately when needed.

In one embodiment, a pressure-increasing device, for example a piston that is hydraulically driven, is provided to increase the pressure in the fluid. With such a dosing speed can be increased. For example, the pressure-increasing device may also include means for increasing the gas pressure in a cylinder containing the liquid and a gas.

With a control device for the pressure-increasing device in which the value detected by the pressure sensor is passed as a feedback signal to the control device, the accuracy of the dosage can be further increased.

• Verbinden des Flüssigkeitsbehälters mit dem Flüssigkeitsspeicher
• Füllen des Flüssigkeitsbehälters mit Flüssigkeit aus dem Flüssigkeitsspeicher,
• Trennen der Verbindung des Flüssigkeitsbehälters mit dem Flüssigkeitsspeicher,
• Erhöhen des Drucks im Flüssigkeitsbehälter zum Ablassen von Flüssigkeit aus der Ablassvorrichtung auf.

The application also relates to a method for dosing liquid with a device according to the application, wherein the device additionally comprises a switch for switchably connecting the liquid container with a liquid storage. The method comprises the steps

• Connecting the liquid container with the liquid storage
• Filling the liquid container with liquid from the liquid storage,
• Separating the connection of the liquid container with the liquid storage,
• Increase the pressure in the liquid container to drain liquid from the discharge device.

With the aid of this method, liquid can be drained without having to move moving parts in the path between the liquid container and the discharge device during draining, as would be the case with conventional outlet valves. As a result, the number of components can be reduced, which reduces the space required and the

It should be noted that even liquids that slowly release gas by decomposition should be dosed. For this it is particularly important that venting steps are provided.

There are embodiments in which, for example, a multi-way valve is provided at the end of the first tube device, so that it is possible to switch over between a plurality of second tube devices, each of which opens into its own outlet device. However, preferably such a multi-way valve is not switched while being drained. This allows a good control of the process by means of a pressure measurement during the discharge process.

In one embodiment, the step of increasing the pressure is performed at least twice, wherein in a first pass the first tube device and the second tube device are flushed and in a second passage a predetermined amount of liquid is metered out.

Thus, the dosing accuracy is increased for the second implementation.

If, during draining, liquid drops from the discharge device in drop or jet form, there is no or very little atomization, which ensures that the liquid does not dissolve in the air but falls into a dosing container.

The application also relates to a method for dosing liquid in a container with a device according to the application. The method includes a step of applying a pressure to the liquid to drain the liquid. The pressure is measured by the pressure sensor and the measured pressure is shown on the display. With this method, it is now possible to observe the dosing of liquid, so that the dosage is reliable and highly accurate.

In addition, the device can be monitored for increased pressures. If these pressures become too great, there is a risk of bursting tubes or hoses. Especially at aggressive and toxic media such as hydrofluoric acid end up bursting hoses surrounding people. Thus, with the method, the safety can be increased.

Preferably, prior to the step of applying pressure to the liquid, a step of venting the liquid is made. In this case, for example, a lot of liquid is drained off before the actual dosing process.

According to another method according to the application, liquids are metered into a container, a device according to the application being used. The method comprises a step of exerting pressure on the liquid for discharging the liquid, the pressure being measured by the pressure sensor and the measured pressure being examined for defect images by means of an electronic evaluation. With this method, the automatic electronic evaluation is provided so that an operator gets the errors reported, for example by short message (SMS) on his mobile phone.

The application also relates to a method of dosing liquids with a device including a liquid container completely filled with liquid, a discharge device and a tube device for passing liquids from the liquid container to the discharge device. A pressure measuring device is provided for measuring the pressure of a liquid inside the tube device, the pressure measuring device having a cavity connected to the interior of the tube device and a pressure sensor for detecting a pressure in the cavity. The method comprises the steps of increasing the pressure on a liquid in the tube device to drain liquid from the discharge device and observing the pressure in the liquid by means of the pressure measuring device.

With the aid of this method it can be checked whether, during the discharge of the liquid, there are air bubbles in the tube device and it is checked whether any liquid is being dispensed or if e.g. a hose is torn or a cylinder is defective.

In one embodiment of the method, one or more steps of draining the liquid are performed before the actual dosing operation. These steps can be used to check the presence of air in the system using pressure measurement.

Before the actual dosing process, in one embodiment, a drop hanging on the discharge device is blown off.

• Verbinden des Flüssigkeitsbehälters (28) mit einem Flüssigkeitsspeicher
• Füllen des Flüssigkeitsbehälters mit Flüssigkeit aus dem Flüssigkeitsspeicher,
• Trennen der Verbindung des Flüssigkeitsbehälters mit dem Flüssigkeitsspeicher,
• Erhöhen des Drucks im Flüssigkeitsbehälter zum Ablassen von Flüssigkeit aus der Ablassvorrichtung, vorzugsweise bis alles Gas aus dem Behaelter verdraengt ist,
• Erneutes Laden des Flüssigkeitsbehälters
• Alle Ventile und Abzweigungen schalten.
• Beliebige Spülvorgänge zur Reinigung, dann neu aufladen.
• Mit einem Teil des Zylindervolumens das Gefäßsystem spülen/entlüften
• Tropfen abtrennen
• Wechsel des Gefäßes oder Spülen des Gefäßes
• Zielvolumen dosieren
• Tropfen abtrennen ins Zielgefäß

An embodiment of the method includes the following steps:

• Connecting the liquid container (28) with a liquid storage
• Filling the liquid container with liquid from the liquid storage,
• Separating the connection of the liquid container with the liquid storage,
• Increasing the pressure in the liquid container to drain liquid from the discharge device, preferably until all the gas has been displaced from the container,
• Reload the liquid container
• All valves and branches switch.
• Any rinses for cleaning, then recharge.
• Use part of the cylinder volume to rinse / vent the vascular system
• Separate drops
• Changing the vessel or rinsing the vessel
• Dose target volume
• Separate drops into the target vessel

Figur 1

zeigt eine Vorrichtung zum Dosieren von Flüssigkeit.

Figur 2

zeigt eine Weiche, die Teil der Vorrichtung aus Figur 1 ist.

Figur 3

zeigt die Weiche aus Figur 2 in Baueinheit mit einem Drucksensor.

Figur 4

zeigt eine Ausführungsform einer Druckmessvorrichtung zum Einsatz in einer Vorrichtung gemäß Figur 1.

Figuren 5 bis 9

zeigen Verläufe von Signalen, die von Drucksensoren in Vorrichtungen gemäß Figur 1 während mehrerer Dosiervorgänge erfasst werden.

The invention will be explained below with reference to the drawings.

FIG. 1

shows a device for metering liquid.

FIG. 2

shows a switch, the part of the device FIG. 1 is.

FIG. 3

shows the switch FIG. 2 in unit with a pressure sensor.

FIG. 4

shows an embodiment of a pressure measuring device for use in a device according to FIG. 1 ,

FIGS. 5 to 9

show waveforms of signals from pressure sensors in devices according to FIG. 1 during several dosing operations are detected.

FIG. 1 shows a device 20 for dosing liquids. The device 20 includes a cylinder 23, a pressure measuring device 25, a first tube device 24, a second tube device 241, which opens into a discharge device 28, and a cup 29. The tube devices 24 and 241 are formed as tubes. In addition, the device includes a switch 500 and a liquid storage 501. The cup 29 can can be changed manually or automatically or it can be used as a stationary vessel, which is rinsed automatically after use.

The discharge device 28 is designed as a tip having an opening diameter of less than 0.4 mm. The discharge device has no moving parts. If the pressure in the liquid 31 does not exceed a certain value, hydrostatic forces in the liquid cause no liquid to fall from the tube devices out of the tip. At elevated pressure, however, gravitational force and the force caused by the pressure exceed the hydrostatic forces, so that liquid emerges from the tip in the form of drops or in the form of a jet. Moving parts in the outlet device would mean the introduction of other materials, so that the other materials could pollute the liquid 31.

The cylinder 23 includes a housing 22 and an externally operable piston rod 21, by means of which a piston surface 222 can be moved in the interior of the housing 22. The interior of the housing 22 is thereby divided into two separate rooms. The space bounded by the surface of the piston surface 222 which has no piston rod is referred to as a liquid container 32 and is connected to the interior of the hose 24. The tube 24 is also referred to as a first tube device and the tube 241 as a second tube device. In an alternative embodiment, the tubes 24 and 241 are replaced by tubes. The liquid container 32 is also connected to a changeover switch 500. This is switchable such that either the liquid container 32 is connected to the liquid storage 501 or that the connection between the liquid container 32 and the liquid storage 501 is disconnected.

The interior 35 of the tube 24 and the tube 241 and the liquid container 32 of the cylinder 23 are filled with a liquid 31, e.g. with a highly reactive liquid such as hydrofluoric HF. The tube 24 leads to the pressure measuring device 25, specifically into a cavity 27, against which a diaphragm, not shown in this figure, of a pressure sensor 26 rests. The tube 24 is completely filled with the liquid 31, from cavity 27, a second tube 241 leads to the tip 28, which is open at the bottom. Below the tip 28 is the cup 29, in which the liquid 31 is metered filled.

To fill liquid metered into a cup 29, a first cup 29 is first led under the tip 28, preferably automatically.

Then, the device must be filled with liquid 31 by filling the liquid container 32 and the tubes 24 and 241 with liquid. For this purpose, the switch 500 is actuated so that the liquid container 32 is connected to the liquid storage 501 such that liquid 31 can flow between the two vessels. The liquid storage 501 was previously filled with liquid, e.g. Hydrofluoric acid, filled.

After forming the connection, the piston rod 21 is lifted, so that the volume of the liquid container 32 increases. Thus, liquid 31 is sucked into the liquid container 32. There is no gas bubble between the liquid 31 and the piston surface 222. Gas in the liquid container increases the risk of gas bubbles in the liquid. Since these reduce the dosing accuracy, gas bubbles should be avoided if possible, and if there should be gas bubbles in the liquid, they should be removed in a controlled manner.

After sucking liquid by lifting the piston rod 21, the switch 500 is closed again, whereby the liquid container 32 is separated from the liquid reservoir 501.

In a further step, to vent the hoses 24 and 241, the piston rod 21 is moved downwards, which is repeated several times in succession. By this movement, some liquid is discharged into the cup 29, with air or other gas, which is located in the liquid 21, from the hoses 24 and 241 and the cavity 27 is pushed out. However, in preferred embodiments, the pressure is not increased so much that the liquid atomises. In the case of atomization, there is the possibility that partially drained liquid will not end up in the cup 29.

Subsequently, any drop hanging on the tip is removed by means of compressed air.

As a next step, either the first cup 29 is rinsed or a second cup 29 is guided under the tip 28.

Then the device is ready for the actual dosing process, in which liquid is discharged into the now located under the top 28 cup 29. The dosage is used, for example, for mixing solutions that are used in the chemical industry for high-precision etching and / or examining floating surfaces. The device is particularly suitable for mixing ultra-trace solutions where the amount of contaminants is close to the detection limit.

Air in liquid is basically compressible. Pressure changes in the liquid can therefore not be detected as accurately as changes in pressure of pure liquid in the presence of air. The more air bubbles are in the liquid, the more compressible volume is in the liquid and changes the course of pressure changes.

The piston rod 21 is pressed down, for example by means of a stepping motor or a magnetic actuator. Thus, the pressure in the liquid 31 increases, so that a portion of the liquid 31 exits through the tip 28 down, after which this part falls into the cup 29. For example, the tip 28 is so fine that it has a diameter of 0.3 mm in a round cross section. During the outflow of liquid, the pressure within the liquid 31, for example by 0.2 bar, increases due to the resistance formed by the tip and the hose line. This change in pressure is detected by the pressure sensor 26 and output, for example, to a display unit, not shown in this figure, on which the course of the pressure over time is displayed.

Alternatively or additionally, the signal curve of the measured pressure is analyzed electronically in an evaluation device with the aid of a fast Fourier transformation. For example, it can be clearly seen on the signal course if there is a blockage in the tube 241 in the flow direction behind the pressure measuring device 25. In this case, the pressure of the liquid increases very strongly, which can be detected by means of the pressure sensor 26.

On the other hand, it can be seen if there are air bubbles in the liquid 31. In this case, changes in pressure are much slower than in a liquid without air bubbles or the pressure curve breaks down when air bubbles eventually pass the tip, since the air bubbles for the bubbles 28, the resistance of the tip is lower than for the liquid.

The dual paths to the cavity 27 through the tubes 24 and 241 serve to flush the cavity 27. Possibly occurring gas bubbles or impurities, resulting for example by detached particles of the hose can not collect in the cavity 27, since they are flushed out of this cavity 27 out. The detached particles may be contaminated by surface contaminants in the production of the Material or from deposition. If the cavity were not rinsed, the contaminants would accumulate in the dead volume and could eventually be flushed out suddenly.

It has also been shown that a flow direction of the liquid should be provided by the two paths. Characterized in that all liquid 31 flows from the liquid container 32, which is to flow to the discharge device 28, through the cavity 27 with a predetermined direction, it is ensured that a flushing takes place. A pressure sensor, which is only connected by a path to a conduit between the liquid container 32 and the discharge device 28, contains a dead volume in which contaminants and in particular air bubbles can be deposited. This would also be the case if there were two paths but they did not define a direction of flow.

In a preferred embodiment, voids are also avoided in the tube devices 24 and 241, for example, by rounding corners.

With the device described, it was possible to achieve an accuracy of less than 0.1 μl for a cylinder with a capacity of 2 ml of liquid, whereby the accuracy is understood to be the standard deviation of the variation of the measurement results from five metering operations. The accuracy measurements were made for seven metering devices. The cylinders and the drive units for the piston of the cylinder came from Metrohm, Herisau, Switzerland.

The impurities are discharged through the tip 28 from the tubing, preferably, of course, into a cup 29 which serves not to mix but to clean the tubing.

FIG. 2 shows a switch 1, the part of the pressure measuring device 25 from FIG. 1 is. The turnout 1 is in FIG. 2 a plan view, shown in a sectional view and in an oblique view. The switch 1 includes a first nipple 6, a second nipple 7 and third nipple 8. The switch 1 also includes a switch housing 2. The nipples 6, 7 and 8 are respectively screwed into the housing by means of a respective thread 18. Inside the switch housing 2 is a cavity 15, which opens into the connections of the nipple 6, 7 and 8, respectively. The nipples 6, 7 and 8 each have cylindrical inner cavities, so that the cavity of the nipple 8 is connected via the cavity 15 of the switch housing 2 both with the cavity of the nipple 6 and with the cavity of the nipple 7.

Hoses can be connected to the nipples 6, 7 and 8 from the outside or hoses can be inserted into the cavities of the nipples 6, 7 and 8.

FIG. 3 shows the pressure measuring device 25 with the switch 1 and the pressure sensor 26. Between the pressure sensor 26 and the switch 1, a hose 9 is provided which connects these two components, the switch 1 and the pressure sensor 26 with each other.

The pressure measuring device 5 includes a housing 4, inside which the cavity 27 is located. The housing 4 has a hollow cylindrical extension 41. The cavity 27 is thus connected via the interior 441 of the extension 41 to the interior 442 of the tube 9. On one side of the cavity 27, a membrane 19 is connected, which is provided between the cavity 27 and a pressure chamber 13 and which bends depending on the pressure in the cavity 27. This is measured in the pressure chamber 31 by means of a piezoelectric sensor not shown in this figure. At this piezoelectric sensor are connected by electrical lines 14, which lead to an evaluation unit 33. Depending on the pressure in the pressure chamber 13 and thus depending on the pressure in the cavity 27, the electrical voltage between the two terminals of the lines 14 increases or decreases.

This electrical voltage is converted in the evaluation unit 33 into a value for the pressure. The calculated pressure is plotted on a display unit 34 over time. In addition, the course of the pressure is stored in a memory 38. In this embodiment, the measured pressure is applied to a control device 35 for controlling the movement of the in FIG. 1 shown piston rod 21 issued.

At the nipple 7, the tube 241 is connected. In the cavity of the nipple 6 of the tube 24, for the sake of clarity in FIG. 3 partially represented as a single stroke. The tube 24 extends through the cavity of the switch housing 2, the interior of the nipple 8, the interior of the tube 9 to the cavity 27 of the pressure sensor 26th

The liquid thus flows from the tube 24 into the cavity 27 and from there into the tube 241. This results in a movement of the liquid in the cavity 27, which causes liquid to pass through the interior 442 of the tube 9, through the cavity 15 of the Switch body 2, flows through the nipple 7 to the tube 241, after which it to the top 28th flows and is drained there. In the switch 1, an O-ring is also provided, which presses below the nipple 8 from the outside against the hose 9, so that it is sealed.

FIG. 4 shows a further embodiment of a pressure measuring device 25. This has a cavity 27, to which the inside of the tube 24 is connected from a first side and the inside of the tube 241 on the other, the first side opposite side. Thus, the cavity 27 is flowed through by the liquid from bottom to top. The cavity 27 is shaped so that it has no corners, since deposits can form in corners for impurities. A pressure sensor 26 is provided laterally between the inlets for the tubes 24 and 241.

FIG. 5 shows an example of the pressure curve during a dosing process. In this case, a metering device with two liquid containers, two tube devices, two pressure measuring devices and eight cups 29 is used. Each of the liquid containers is connectable via a multiplexer to each of the eight cups, which means that an 8 to 1 multiplexer is provided downstream of the pressure measuring device so that one of the eight cups can be filled from each liquid container.

The curve marked with the triangle denotes a dosing process from the first liquid container and the curve marked with a square indicates a second dosing process from the second liquid container. In the diagram, the pressure in millibars is plotted over the time in seconds. The two curves show the two different metering operations, which are independent of each other but occur simultaneously. The baseline of the two curves is slightly different, this is because the absolute values of the sensor were calibrated differently, which was left in favor of a better representation.

The curve marked with a triangle shows a dosing process that is inconspicuous, from which it is concluded that there was no error. Whenever fluid is drained, the pressure inside hoses 24 and 241 increases by about 100 mbar. This should actually be done in the device whose pressure curve is marked with a rectangle. However, it is noticeable that the pressure in the first discharge increases by more than 200 millibars. From this it can be concluded that there was a blockage in the discharge device leading to a higher resistance for the liquid and thus to an increased pressure leads. In subsequent draining operations this blocking is no longer visible.

FIG. 6 shows the course of another dosing process as in FIG. 5 after the hose that had been clogged was replaced. It is noticeable that the pressure on the curve marked with the rectangle only increases slowly. This is because air was previously in the hose and the level of fluid in the hoses is only rising slowly. This means that the capillaries have filled only during this dosing. The same would result if the metering device is moved up during the dumping process.

FIG. 7 shows the course of the pressure inside the liquid of the tube device during a venting process. The curve drawn with the rectangle shows how the pressure increases in two phases and then decreases again. In the lower picture it is shown that there are two more of these phases, whereby before each of these phases a short pressure pulse can be seen in each case upwards. At about 230 seconds, the piston rod is guided down in the cylinder and thus increases the pressure in the liquid. However, the pressure increases only slowly, ie over a period of about 40 seconds. This is because there are air bubbles in the fluid that are compressible.

In the method shown, a device is used which, in addition to the device disclosed in U.S. Pat FIG. 1 is shown, a filling vessel and a valve. A valve is adjustable so that the liquid container is connected either to the contents of the filling vessel or to the interior of the tube 24. For filling the liquid container, it is connected to the interior of the filling vessel, wherein the piston rod is lifted. To drain the liquid, the liquid container is connected to the interior of the tube 24 and the piston rod is lowered.

At about 320 seconds, the valve on the piston is switched so that the liquid container is no longer connected to the liquid in the tube device, but with the liquid inside the filling vessel. Subsequently, the piston is lifted, so that again liquid flows from the filling vessel into the liquid container of the cylinder.

From the time 420 seconds, the valve is switched so that the liquid container of the cylinder is reconnected to the interior of the tube device. Subsequently, the piston is lowered again, so that the pressure in the liquid is increased.

At time 780 seconds, a short peak is seen. This is because the piston is driven briefly down to its normal working range from top to bottom, before being completely lowered at 785 seconds. It can therefore be seen that the increase in pressure in the fluid is very fast, much faster than in the pressure increases at 250 and at 450 seconds. The curve from 980 seconds approximately corresponds to the curve from 780 seconds. From the pressure traces, the user could learn that the present device required three venting operations to vent the cylinder and hoses. Depending on the severity of the procedure, four or five venting operations may be required.

FIG. 8 shows a further course of pressure signals in a group of Dosiervorgängen. It turns out that the pressure changes that are supposed to take place every 10,000 seconds do not occur any longer from the time of 6,000 seconds on the curve marked with the triangle. This was due to the fact that a clutch to control the piston of the cylinder was broken and thus no liquid was drained. Such serious errors can be detected with the help of the printing device.

FIG. 9 shows the pressure curve during a complete dosing process with rinsing and venting. Here several liquids are simultaneously discharged into a cup, each with different cylinders and with different tube devices. At time 520 seconds, one peak can be seen downwards. In this dosing process, the piston is driven slightly upwards at this time in order to avoid that drops that can form after a drop of a drop due to minimal fluctuations in the further course of time and still fall. Thus, liquid is drawn back into the tube by means of negative pressure at the discharge device. This prevents changes in the concentration of the mixture in the cup due to unintentional discharge in stationary vessels for extended periods of time.

LIST OF REFERENCE NUMBERS

1

switch

2

soft housing

4

casing

5

sleeve

6

nipple

7

nipple

8th

nipple

9

tube

10

liquid

13

pressure chamber

14

cables

15

cavity

16

O-ring

18

thread

19

membrane

20

contraption

21

Kolbe rod

22

piston housing

23

cylinder

24

tube

25

Pressure measuring device

26

pressure sensor

27

cavity

28

top

29

cups

31

liquid

32

liquid container

33

evaluation

34

display device

35

regulating device

36

Interior

38

Storage

41

renewal

241

tube

242

tube

441

Inner

442

Inner

500

switch

501

liquid storage

Claims (15)

1. Device (20) for dosing a liquid (31), comprising

   - a liquid container (32);

   - a draining device (28);

   - a pressure measuring device (25) with a cavity (27) and a pressure sensor (26) for detecting pressure in the cavity (27);

   - a first pipe device (24) for guiding liquid (31) from the liquid container (32) through the interior (35) of the first pipe device (24) to the cavity (27); and

   - a second pipe device (241) for guiding liquid (31) from the cavity (27) through the interior (35) of the second pipe device (241) to the draining device (28);

   - wherein the device is configured to drain liquid (31) from the liquid container (32) through the draining device (28);
   characterized by

   - a liquid storage (501); and

   - a switch (500), which can be switched in such a way that either the liquid container (32) is connected to the liquid storage (501) or that the connection between liquid container (32) and liquid storage (501) is separated;

   - wherein the device is configured in such a way that by actuating the switch (500), the liquid container (32) is connected to the liquid storage (501) in such a way that the liquid container (32) and the pipe connections (24, 241) are filled with liquid (31); and

   - wherein the device is configured in such a way that all liquid (31) flowing from the liquid container (32) to the draining device (28) flows through the cavity (27) with a predetermined direction.
2. Device according to claim 1, wherein the liquid container (32) is fully filled with liquid (31).
3. Device according to claim 1 or 2, wherein the first pipe device (24) contains a hose that opens into the cavity (27).
4. Device according to one of claims 1 to 3, wherein the draining device (28) does not comprise any moveable parts.
5. Device according to one of claims 1 to 4, wherein the draining device (28) has a downward-opened tip with an opening cross-section of less than 0.4 mm.
6. Device according to one of claims 1 to 6, wherein the pressure sensor (26) contains a piezoelectric element.
7. Device according to one of claims 1 to 6, wherein the signals detected by the pressure sensor (26) are electronically interpreted in an evaluation unit (33) and error messages are output in accordance with the signal courses.
8. Device according to one of claims 1 to 7, wherein a pressure increasing device (21) for increasing the pressure of the liquid (31) is provided in the liquid container (32).
9. Device according to claim 8, wherein a regulation device for regulating the pressure increasing device (21) is provided, wherein the value detected by the pressure sensor (26) is supplied to the regulation device as a feedback signal.
10. Method for dosing liquids (31), with a device according to one of claims 1 to 9, wherein the method comprises the following steps:

    - connecting the liquid container (32) with the liquid storage (501),

    - filling the liquid container (32) with liquid (31) from the liquid storage (501),

    - disconnecting the connection of the liquid container (32) with the liquid storage (501), and

    - increasing the pressure in the liquid container (32) for draining liquid (31) from the draining device (28).
11. Device according to claim 10, wherein no parts are moved during the step of increasing the pressure in the device in the path between the liquid container (32) and the draining device (28).
12. Device according to claim 10 or 11, wherein the step of increasing the pressure is conducted at least twice, wherein the first pipe device (24) and the second pipe device (242) are purged in a first execution, and a predetermined amount of liquid (31) is drained in a dosed manner in a second execution.
13. Method according to any one of claims 10 to 12, wherein during the draining of liquid (31) from the draining device (28), liquid drops out in the form of droplets or jets.
14. Method for dosing liquid (31) into a container with a device according to any one of claims 1 to 9,

    - wherein the method contains a step of exerting a pressure on to the liquid (31) for draining the liquid (31),

    - wherein the pressure is measured by the pressure sensor (26), and the measured pressure is displayed on a display device (34), and

    - wherein prior to the exertion of pressure on to the liquid (31), pressure and negative pressure are alternately exerted on to the liquid (31) for de-aerating the liquid (31).
15. Method according to claim 14, wherein prior to the dosing process into a target vessel, one or multiple steps of draining the liquid (31) are provided for deaeration, and wherein optionally a droplet suspended on the draining device (28) is blown-off prior to the dosing process.

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