WO2009121567A2

WO2009121567A2 - Device and method for the exact metering of fluids

Info

Publication number: WO2009121567A2
Application number: PCT/EP2009/002350
Authority: WO
Inventors: Frank Bartels; Markus Rawert
Original assignee: Bartels Mikrotechnik Gmbh
Priority date: 2008-03-31
Filing date: 2009-03-31
Publication date: 2009-10-08
Also published as: WO2009121567A3; DE102008016513B4; DE102008016513A1

Abstract

The present invention relates to the exact metering of fluids, wherein said fluids may have different viscosities, temperatures, densities, and the like, without the accuracy of the metering achievable by the invention being negatively influence thereby. The device according to the invention comprises at least the following key elements: a bi-directionally delivering pump device (2); a metering tube (3) having a known geometry; an optical detector (4) for determining the fluid level; wherein the pump device (2) is disposed such that the fluid (F) to be metered can be delivered through the metering tube (3), and wherein the optical detector (4) is disposed such that the position of the fluid front (7) of the fluid (F) to be metered can be detected at least at two readout points (8, 8') of the metering tube (3). The invention further discloses a method for the exact metering of fluids, which can be carried out most preferably utilizing the device according to the invention.

Description

Device and method for exact dosing of liquids

introduction

The present invention relates to an apparatus and method for precise metering, and more particularly to the removal and subsequent release of a predetermined amount of a fluid.

In particular, the present invention also relates to an apparatus and method for accurately metering liquids, which liquids may have different viscosities, temperatures, densities and the like, without adversely affecting the dosage accuracy achievable with the invention.

State of the art and disadvantages

The dosing of liquids plays a decisive role in a large number of technical fields. For example, when joining components, it is important to apply a precisely metered amount of adhesive since the strength of the bond will be optimal in the case of too little or too much applied adhesive. This problem is compounded in the case of multicomponent adhesives, in which the mixing ratio of the individual components is precisely determined and must therefore be observed. Another field of application in which the exact dosing of liquids is of the utmost importance is represented by the life sciences (English: "Lifesciences"). Since it is often necessary to handle small and very small amounts of liquid, this results in particularly low tolerated tolerances in the application, mixing, or extracting liquids or liquid mixtures.

The trend towards ever-increasing miniaturization in many areas of technology therefore makes it increasingly necessary, especially small and very small ones

Safe, reproducible and, above all, very accurate metering of liquid quantities. For this purpose, a variety of different from the prior art Devices and methods are known, of which some will be listed below by way of example.

First of all, manually operated devices for taking and dosing small amounts of liquid, which are commonly used in e.g. find use in laboratories. When using manually operated so-called pipettes, as disclosed for example in the document DE A 1 598 629, the accuracy of the dosage of the surface tension of the withdrawn liquid, the capillary forces acting on the inside and outside of the pipette wall, and the Problem of attachment or retention of microdroplets determined at the outer end of the pipette. Even in the event that such a pipette is operated automatically, these problems essentially remain.

Another problem with the use of such manual devices is the dependency of the dosage result on the respective operator. For this reason, it is often attempted to improve the reproducibility of the dosage result through the use of automated devices.

A first example of an automated microdosing device is disclosed, for example, in the patent DE 101 53 708 B4. This microdosing device comprises a nozzle body with a cavity in which a fluid to be dosed is present. The dosing operation is carried out by means of a displacement body which is attached to an actuator. This displacement body reduces the volume in the interior of the cavity, so that the fluid to be metered displaced from this and discharged from a nozzle. The accuracy with which the fluid to be dispensed is dispensed from the nozzle depends largely on the accuracy with which the corresponding actuator can be controlled. Furthermore, it is imperative to store the moving parts of the device without clearance and gap, so that no liquid as possible penetrate into corresponding column and thus can distort the volume to be dosed. Finally, such a device due to its structural conditions only for the output of a certain, limited by the size of the cavity upwardly limited amount of liquid in a position, since after a complete emptying of the void volume this first again with must be filled from a reservoir nachfließenden, to be dosed liquid before a re-issue of the liquid volume can be done. Accordingly, a device of the type shown is not suitable for the continuous dispensing of larger or any desired quantities of liquids to be dispensed.

The same disadvantage is shown in the patent application US 5,512,046. Here, the control of the dosage takes place on the basis of optically operating counters, which determines the number of released by the metering device and it traverses this in free fall traversing drops. In the case of deviating from the setpoint number of drops, a corresponding control valve is increased or decreased. The advantage here is the use of an optical and thus non-contact principle to control the dispensed drops. The main disadvantage of the relevant invention is to be able to apply the volume of a single drop as the smallest theoretically dosable amount. In addition, the device in question also does not recognize when the volume of the individual drops changes due to temperature fluctuations.

Another example of the use of optical technologies in the context of metering devices is disclosed in the publication DE 102 42410 A1, which comprises a capillary or a needle in conjunction with an image recording device for applying a fluid medium to a substrate, and also an image processing device assigned thereto , During the application of the liquid to be metered, which can be applied only in the form of individual drops, the image processing device records the drop shape resulting during the application process and analyzes it. Based on the analysis, the distance of the dispensing needle and the substrate is readjusted as needed. A major disadvantage of this approach is the need to analyze the shape of each drop by means of a relatively sophisticated image processing technique. Accordingly, the metering of a continuous stream of liquid is not possible. Similarly, the effort to analyze the drop shapes and readjust the distance, not insignificant. Another problem addressed by various technologies in the metering of liquids is the dependence of the liquid volume on environmental parameters, in particular the temperature.

This problem is treated, for example, in the published patent application DE 103 56 805 A1. In particular, the invention presented there concerns the problem in connection with the metering of liquid in motor vehicles. The invention proposes first of all to estimate the liquid temperature and thus to determine a correction with which the control signal given on a metering pump is supplemented, so that the metering pump generates identical quantities of liquid on the basis of identical setting value input signals independently of the metering pump

Liquid temperature supplies. However, such a method requires always to have information about the liquid temperature available. It also disregards that in a dosage of different liquids also each have different correction factors must be present, which are incidentally previously, for example by means of appropriate experiments, to determine.

Finally, a particular difficulty is to be able to meter a plurality of liquids by means of one and the same device or using one and the same method in succession, if these liquids with respect to important parameters (temperature, density, viscosity, surface tension) from each other differ. One way to address this problem is to accurately analyze all liquids to be dosed with a particular device in advance and to place the doses that can be achieved under certain standard conditions into a corresponding (electronic) table. During the actual dosing process, these standard values can then be taken from the corresponding table and fed to a control device. However, this approach only leads to success if every one of the possible liquids to be pumped is properly detected in advance. Conversely, this results in a non-employability of a device in the event that the corresponding liquid to be dosed has not previously been tabulated. Another disadvantage is because of the expense involved to include only a certain number of parameter combinations, so that interpolation between the corresponding positions of the norm values must be done. It is also necessary to tell the device before the dosing process which liquid is currently to be dosed so that the corresponding parameters can be loaded. Finally, the corresponding method fails even if mixtures of liquids which were previously only detected individually are conveyed in combination, unless a renewed detection of the corresponding parameters of the liquid mixture takes place here.

In view of the progressive miniaturization in technology, the devices shown above are also only partially suitable for integration into corresponding, very low volumes available systems, since the space occupied by them is sometimes considerable.

Object of the invention and solution

It is therefore an object of the present invention to provide an apparatus and a method which are suitable for overcoming the described disadvantages of the prior art. In particular, the invention should be suitable for precisely metering liquids which may have different viscosities, temperatures, densities and the like, without adversely affecting the accuracy of the dosage achievable with the invention. The invention should provide reliable and reproducible results as independent as possible of the liquid to be dispensed, its parameters, as well as the amount to be dispensed. The effort for calibration of the device according to the invention when dosing a new liquid should be kept to a minimum.

The device according to the invention and the method according to the invention should also be independent of environmental parameters, such as pressure or temperature, insofar as a corresponding readjustment with the least possible effort and in an automated manner is possible. In particular, the possibility should be given, quasi-continuously a virtually unlimited amount of liquid high Promote precisely dosed. The measurement of the delivery rate of the liquid to be dispensed should be done without contact, but at the same time with the simplest possible and thus cost-effective means and without loss of time. Finally, the device according to the invention should offer good possibilities for space-saving integration, in particular in miniaturized metering systems.

The above objects are achieved by the features of the device according to the invention according to claim 1 and the features of the method according to claim 11.

Further preferred embodiments can be found in the dependent claims and the following detailed description and the figures.

description

The device according to the invention serves the exact dosing of liquids, in particular a sequential plurality of liquids, which differ by their liquid parameters. The device according to the invention comprises at least the following essential elements:

a pumping device; a metering tube of known geometry; a detector for determining the fluid level.

According to the invention, the pumping device is arranged so that the liquid to be metered can be conveyed through the metering tube. The pumping device may preferably be a micropump, and more preferably a piezo-driven micromembrane pump. According to one embodiment, the micropump may be constructed so as to allow unidirectional or bidirectional conveyance, for example by means of a diaphragm and corresponding valves.

The metering tube is designed such that its geometry is known very precisely. This means that in particular the inner cross section or the inner diameter of the metering tube is exactly predetermined. According to the invention is also the distance between at least two predetermined positions exactly determinable along the longitudinal extent of the metering tube. Particularly preferably, the metering tube has the same cross section in its interior over its entire longitudinal extent. It advantageously has a cylindrical cross-section, but it can also be designed differently, for example, square.

According to the invention, the detector is arranged such that the position of a liquid front of the liquid to be metered can be detected at at least one read-out point of the metering tube. By means of the detector for determining the liquid level, the position of the liquid front of the liquid to be metered, which is conveyed through the metering tube, is determined according to the invention. According to one embodiment, the detector makes it possible to determine a position of the liquid front in the interior of the detector tube. According to a preferred embodiment, the detector merely enables the detection of the presence of the liquid front at one or more predetermined locations located along the length of the metering tube.

According to a preferred first embodiment of the device according to the invention this further comprises at least one valve, wherein at least one valve is arranged so that the flow of liquid flowing through the metering tube is interrupted so that when closing the valve, the existing liquid volume in the metering tube not by adding further liquid can be increased. Accordingly, and because the volume of the metering tube is known in particular between the valve and the at least one read-out location, there is thus a precisely determined volume of liquid in the relevant part of the metering tube, which can then be metered. For this purpose, by means of the valve, an external connection can be added, which is preferably connected to a gas and more preferably to the ambient air. Finally, according to this embodiment, the pumping device is arranged downstream of the valve, so that it can be conveyed with it optionally to metered liquid or an external medium. When switching the valve to the external connection, only the medium flowing through the external connection (which may be advantageous, in particular, gas) can be conveyed into the metering tube. By appropriate conveying after switching is therefore the first in the dosing available and previously exactly promoted certain volumes of liquid out of the dosing. It is irrelevant that the pumping device is arranged downstream of the valve, since the volume of the pumping device is not variable and, accordingly, can easily be added to the volume of the metering tube or of the section between the valve and the at least one read-out point. As soon as the exact amount of liquid has been completely conveyed out of the dosing tube, only the external medium is conveyed; in the case of air or a protective gas, which is not miscible with the liquid, thus a precisely predetermined amount of liquid to be dosed and dosed for example in a reservoir.

The first embodiment of the device according to the invention described so far is based on the exact determinability of a volume, which is first completely filled with a liquid to be metered and then also completely emptied.

According to an advantageous modification of the first embodiment of the present invention, a suitable mechanism may be provided which allows to move the detector of the determination of the liquid front at least one and advantageously two or more predetermined locations axially to the metering tube, so that a device for adjustment and calibration of the predetermined volume of the liquid to be dispensed is provided.

In the following, a device is described according to an advantageous second embodiment of the present invention, which is designed such that in addition the time is determined, which requires the liquid front of the liquid to be metered when passing through the metering tube to cover a precisely known distance. The inventively provided known geometry is therefore also given in the following examples.

According to a preferred embodiment of the device according to the invention, this further comprises a time measuring device. By means of this time measuring device, the time is determined, which requires the liquid front of a funded through the metering, to be metered liquid to a predetermined

Travel distance in the interior of the metering tube. Particularly preferred The time measuring device, the corresponding start and stop signals from the inventively also be provided detector, so according to the invention can be controlled by the detector.

In the following, a preferred embodiment of the detector of the device according to the invention will be described in more detail, according to which the detector is designed as an optical detector. First, this optical detector comprises a light source, which is preferably a white light emitter. It further comprises at least one illumination fiber for transmitting the light to the metering tube and a detector fiber for returning the light from the metering tube, as well as means for collecting the light.

The light source according to the invention is arranged so that the light can be introduced into a first end of the illumination fiber. In order to maximize the corresponding luminous efficacy, it may be preferable to provide corresponding mirrors or, in the case of one or more light-emitting diodes, a correspondingly exact alignment of the light source in the direction of the illumination fiber. The illumination fiber in turn is arranged so that a second end thereof is in optical communication with a first end of the detector fiber. "Optical connection" in this context means that a change in the light which emerges from the second end of the illumination fiber simultaneously leads to a change in the light which is radiated into the first end of the detector fiber

For example, bonding may preferably be accomplished by aligning the fiber axes of the second end of the illumination fiber and the first end of the detector fiber substantially coaxially. However, it is also possible to bring about the optical connection according to the invention via mirrors, lenses and the like.

The metering tube is inventively arranged so that this optical connection can be influenced depending on the filling of the metering tube. According to a particularly preferred embodiment, therefore, the metering tube is arranged in the beam path of the optical connection, so that a change in the transparency of the metering tube leads to a change in the optical connection. Such

Above all, change will always occur when the initially empty dosing tube is filled with liquid, or the already filled dosing tube is emptied again. To In another embodiment, the optical connection is influenced without the dosing tube being arranged in the beam path. Such influencing can be effected in particular by electrical and / or electronic aids, such as conductivity sensors on the inner wall of the metering tube in connection with, for example, electrically adjustable mirrors, which are located in the optical path of the optical connection. A point at which the metering tube interacts with an optical connection is also referred to below as the readout point. Although the metering tube particularly preferably has the same cross-section in its interior over its entire longitudinal extent, it may also be particularly preferred if the metering tube interacts with the respective optical connection at precisely those points where it generally interacts with a read-out point is arranged, has a cross-section, which further improves the accuracy of a detection of the liquid front. This can be done, for example, by reducing the cross-section at the corresponding points in comparison to the rest of the metering tube, so that the liquid flowing through the metering tube passes the corresponding read-out point faster.

Finally, it is inventively provided that the means for collecting the light is arranged so that the light from a second end of the detector fiber in the means for collecting the colored light can be irradiated. By means of the means for collecting the light is therefore the light, which is passed from the light source through the illumination fiber on the readout point (s) and the detector fiber, for example, in its intensity and / or wavelength detectable. This makes it possible according to the invention to detect an influence on the optical connection from the metering tube, as is caused, for example, during the filling thereof.

According to a preferred embodiment of the device according to the invention, the optical detector also comprises color filters for the decomposition of, for example, white light into colored components, which are then separately detectable by the means for capturing the light. This embodiment is advantageous if the position of the liquid front is to be detectable at two (or more) spaced locations (readout points) of the metering tube. Such a detection would initially mean that in each case two illumination fibers and two detector fibers would have to be present, each of which a combination of the same would be assigned to a corresponding readout. The arrangement according to the invention of different color filters, which are assigned to the corresponding read-out points and influence the corresponding optical connection, can be used to precisely determine which read-out location supplies a specific signal to the detector, even when the individual detector fibers are brought together behind the dosing tube a single detector fiber can pass a plurality of different wavelengths side by side without interfering with each other.

According to a particularly preferred embodiment, it is therefore provided that the illumination fiber and / or the detector fiber of the optical detector each consist of a main fiber, which in parts can be divided into several individual fibers, and the areas of divided Einzelfasem are each arranged on the metering tube that the optical Connection of the individual fibers of both main fibers can be influenced by the filling of the metering tube, and possibly existing color filters are arranged so that they are in the region of the divided individual fibers. With such a construction, the number of leading away from the lighting or to the detector leading individual fibers can be advantageously minimized, resulting in particular advantages in terms of the volume and / or the manufacturing cost and complexity of the device. Even in the case of a large number of read-out points, in each case only a single main fiber can be connected to the illumination or to the detector. In particular, in the event that the illumination and / or the detector is or are arranged at a greater spatial distance from the metering tube, such a minimization of the number of fibers for the overall volume is of great advantage.

According to a further preferred embodiment of the device according to the invention, this comprises a plurality of read-out points and associated detector fibers, wherein at least the detector fiber and particularly preferably the illumination fiber, as described above, is divided into individual fibers in the region of the dosing tube. However, the device does not have color filters or similar aids that allow discrimination of the signals generated by the individual readout sites. With others Although the device for capturing the light "knows" that the liquid front passes through a read-out point, but not which of the read-out points has been passed, such an arrangement can also be used for exact dispensing by means of a variation of the method according to the invention, as described below.

It is clear that the above-described detector according to the invention of the second embodiment of the present invention can also be provided in the first embodiment of the present invention, wherein also in the first and in the second embodiment, a suitable mechanism may be provided which allows to displace the detector of liquid front detection at least one and advantageously two or more predetermined locations axially to the metering tube so as to provide a means for adjusting and calibrating the predetermined volume of liquid to be dispensed.

According to a further preferred embodiment of the device according to the invention, the pumping device is present as a bidirectionally conveying pumping device and consists of two counter-rotating, unidirectionally conveying pumps. These individual, each unidirectionally conveying pumps can be arranged in series or parallel in the fluid flow, each allowing an oppositely directed promotion of the liquid to be dispensed. The provision of two unidirectional pumps has the advantage that the failure of one of the two pumps can be more cost effectively remedied since a single unidirectional pump is usually less expensive than a more complex bidirectional pump.

It is particularly preferred that the unidirectionally conveying pumps are arranged in series.

Also particularly preferred is an embodiment of the device according to the invention, according to which the detector is arranged so that the position of the liquid front of the liquid to be metered at three readout points of the dosing tube is detectable. In this way, it becomes possible to have the measurement method to be described later not only on one route, namely, between the first and second readout points, but also on a second one Comparative route, namely between the second and the third readout to perform. In this way, a comparison value can be obtained, which must be approximately identical to the first value during normal operation of the device. A deviation of the two values from each other, however, indicates a malfunction.

It is also possible, in particular with regard to the embodiment described above, according to which the liquid flow is interrupted by a valve and instead replaced by an external fluid to provide several separate metering volumes, for example by spaced differently spaced readout points, and / or by different Internal cross sections of the dosing tube between the individual readout points. Depending on the selection of the selection point pair, a different metering volume determined by the geometric boundary conditions can be selected. In this context, the closing level of the valve can also be regarded as a first read-out point, between which a precisely determinable volume is provided according to the invention in conjunction with at least one further read-out point.

According to a further embodiment of the device according to the invention, this also comprises a drive unit. This drive unit, in turn, includes inputs for signals of the time measuring device (if present) and the detector, and an input device for setting the desired dosage, for example by an operator, and also an output unit for controlling the pumping device, and a computing device for determining the driving time for the pumping device. Preferred as such a drive unit is a commercially available

Personal computer, which is equipped with the appropriate interfaces used. However, the corresponding functions are particularly preferably combined in a housing of small construction volume.

In addition, it is provided according to the invention that the device comprises a reservoir and / or a metering vessel, wherein the reservoir holds the liquid to be metered ready, which is then discharged by means of the device according to the invention in the metering vessel. Preferably, the metering vessel also be placed on a weighing device, so that the mass of the amount of liquid delivered into the dosing can be controlled.

The invention also provides a method for the exact dosing of liquids, which is particularly preferably carried out using the abovementioned devices according to the invention. The inventive method is based on the fact that the direct determination of a variable volume or a flow rate may be complicated, the determination of a fixed volume and possibly the time required for a liquid front to go through a predetermined distance, however, very simple and exactly possible. By using the awareness of a fixed volume, possibly in conjunction with the time measurement, as quality-determining parameters, there is the advantage of a cost-effective device and a robust method.

In the following, both variants of the method according to the invention are described, namely both a first embodiment, according to which only an exactly determinable volume must be present, and a second embodiment, according to which additionally a time measurement must be carried out.

According to a first embodiment, the method according to the invention accordingly comprises the following steps:

(1) Specifying the amount X of a liquid to be dosed (F); (2) switching on a unidirectionally conveying pump (2 ') and conveying the liquid to be metered (F) through a metering tube (3) in the direction of an output 0');

(3) continuously detecting the presence of the liquid front (7) of the liquid to be metered (F) in the metering tube (3) at a read-out point (8); (4) switching off the unidirectionally conveying pump (2 ') as soon as the liquid front (7) reaches the read-out point (8);

(5) switching over a valve (6), so that by means of the unidirectional pump (2 ') instead of the liquid to be dosed (F), an external fluid (F') in the dosing tube (3) can be conveyed; (6) reconnecting the unidirectional pump (2 ') and pumping the external fluid (F') into the metering tube (3) so that it passes the fluid (F) to be metered through the metering tube (3) and out of the outlet (F) 3 ¹ ) of the metering tube (3) also pushes. As a result of the knowledge of the volume according to the invention, which is initially filled with the liquid to be metered, the volume of liquid correspondingly located in this volume can also be determined. By subsequently conveying external fluid, in particular gas, such as particularly preferably air or inert gas, the metered (metered) volume of liquid is pushed out of the metering tube. If the external fluid and the liquid to be metered are immiscible, an exact metering of the liquid can take place in this way.

The above-described first embodiment of the method according to the invention is shown schematically in FIG. 3, which will be understood by those skilled in the art in conjunction with FIG. 1 and the foregoing without further description, it being understood that the steps of the above process Any number of times are repeatable, so that a known amount of liquid can be delivered

It is clear that due to the necessity of the first variant of the method according to the invention described here, to completely empty the metering volume, the resolution of the smallest meterable amount is geometrically determined and thus limited. However, in the case of correspondingly smaller cross sections of the metering tube (capillary) and short path lengths between the readout points, this resolution can already be sufficiently fine.

According to an advantageous modification of the first embodiment of the method according to the invention, a suitable mechanism can be provided, which allows the detector of the determination of the liquid front at least one and advantageously two or more predetermined locations to move axially to the metering tube, so that a method for adjustment and calibration of the predetermined volume of the liquid to be dispensed is feasible. However, it may be desirable to dose even smaller amounts than is possible with the method described above. It may also or additionally be desired to be able to provide a true continuous delivery of the liquid.

According to a particularly advantageous second embodiment, the method according to the invention therefore comprises the following steps, the pump device preferably being a bidirectionally conveying pump device:

(a) setting the amount of a liquid to be dosed;

(B) switching on a pumping device and conveying the liquid to be metered through the metering tube in the direction of the output;

(c) continuously detecting the presence of the liquid front of the liquid to be metered in the metering tube at a first readout location;

(d) starting a time measuring device as soon as the liquid front reaches the first read-out location;

(e) continuously detecting the presence of the liquid front of the liquid to be metered in the metering tube at a second readout location;

(f) stopping the time measuring device as soon as the liquid front reaches the second read-out location;

(g) turning off the pumping device;

(h) calculating the delivery rate of the fluid from the quotient of the volume between the first and second readout locations and the time measured by the time measurement device;

(i) calculating the time necessary to convey the predetermined amount of the liquid;

(j) reconnecting the pumping device and conveying the liquid to be metered through the metering tube over a period in which, while maintaining the previously calculated delivery rate, both the filling volume between the second readout and the output of the dosing tube, as well as the volume of the amount of liquid to be dispensed is promoted.

The predetermining of the amount of a liquid to be metered, which is specified in step (a), can be carried out, for example, by means of an input device which can be assigned to a drive unit. In case of a continuous

Promotion of the liquid to be dispensed, it makes sense if the specification is stored in a memory unit, from which it can be retrieved at any time.

A particularly important step is the step (h), in which the delivery rate of the liquid is determined very accurately. Since the geometry of the metering tube is known exactly, and also the distance between the first and the second

Reading point is known exactly, the corresponding volume between the two readout points can also be determined exactly. Now, if the time it takes for the liquid conveyed in the metering tube forward (in the direction of the outlet) to pass from the first to the second read-out location is known, then the delivery rate can be determined from the time and the volume. The determination of the delivery rate is very easy and fast in this way. In addition to a first determination of the flow rate necessary for exact metering when using a new fluid, which is usually accompanied by changes in the fluid parameters, due to the speed and simplicity of the method according to the invention, the delivery rate can, in principle, be repeated before each metering operation. In this way, temperature and pressure fluctuations that are difficult to exclude during normal operation, can be detected before the actual dosage, for example, in a metering, takes place. By determining the new delivery rate, it is very easy according to the invention to precisely determine the appropriate time required for conveying the liquid to be metered through the remainder of the metering tube (step (i), (j)). Likewise, with the new delivery rate from reaching the output of the metering tube exactly that amount can be output that was also desired and specified.

The just described embodiment of the method uses the

Distinguishability of the signal of the first from a second readout. As already mentioned above, it is also possible without the knowledge of the origin of the respective signal to carry out the inventive method and in particular the determination of the flow rate. According to a modification of the embodiment of the method according to the invention just described, only one counter is needed for this purpose, which assigns a rising index to a signal arriving in the drive unit to a read-out location. Because the

Liquid front during the steps (b) to (f) from the end facing away from the exit is conveyed to the end at which the output is and never arrive two signals simultaneously, since the read-out points are spaced from each other first signal to be uniquely assigned to the first read-out station, etc. However, it is to be ensured after this modification that the liquid front is placed at or before the first read-out point before starting a new dosing or calibration process (see below). This can be done, for example, by conveying the liquid for a sufficiently long time until it can safely be assumed that it has passed the first read-out point. Alternatively, the counter can also be used in a return feed, in order to correctly assign the corresponding signals or the disappearance of the same when emptying the metering tube at the corresponding readout point.

The method according to the invention can be supplemented with particular preference by the following steps, which counteract dripping of the liquid to be metered, which is frequently encountered in the prior art, from the outlet of a metering tube:

(k) operating the bidirectionally conveying pumping device in the direction away from the outlet and returning the liquid to be metered into the metering tube;

(I) continuously detecting the liquid level in the metering tube at a second readout location;

(m) switching off the bi-directionally conveying pumping device as soon as the liquid front reaches the second read-out point.

In other words, after the dosing process, the liquid is withdrawn into the metering tube, for which purpose the bidirectionally conveying Pumping device is used in the return. In order to arrive at a defined initial state for the next dosing process, the process of Rückfördems stops just in the moment in which the liquid front of the withdrawn to be dosed liquid passes the second read-out. This ensures that the exact position of the liquid front is known, so that the following dosing process can begin with a defined initial state.

Also particularly preferred is a variation of the last-described steps to the effect that the return promotion takes place somewhat beyond the last read-out point, and before the beginning of the next dosing the liquid front is again placed exactly at the second read-out location by means of the bidirectionally conveying pumping device and stopped there. This makes it possible according to the invention to compensate for any fluctuations in the volume of the liquid to be metered in the interior of the metering tube, for example due to temperature changes. If the liquid front is located in the region between the first and the second read-out location, and if its position changes due to a temperature or other change in the volume of the liquid (for example due to unintentional pumping of the pumping device), it is ensured in any case before the next dosing process Liquid front is first promoted to the second readout point and thus to a defined location. It should be noted, however, that with a change in the volume of the fluid, the delivery rate may also change, and therefore, depending on the specific reason for the volume change, it is advantageous to repeat a complete calibration procedure as described below.

Accordingly, it is particularly preferred to provide a calibration process for the method according to the invention, in which the liquid to be metered is returned in the direction away from the exit for calibration until the liquid front reaches or slightly exceeds the first read-out point, and then the steps (b ) to (h) so as to obtain the current delivery rate. This sequence of steps thus serves a repetition of the time measurement, which requires the liquid to be metered during its promotion by means of the pumping device to from the first to the second Reading point to be promoted forward. Since the remaining parameters necessary for calculating the delivery rate (geometry of the metering tube) have not changed, the delivery rate can be recalculated based on the renewed time measurement and, if necessary, compared with the old, already calculated delivery rate. In the event of a deviation then the corresponding new value for the delivery rate must be used for further dosing.

According to a further, particularly preferred embodiment of the method according to the invention, this offers the possibility, during the calibration of the not only one, but two paths, which are respectively limited by the corresponding read-out points, to the time and thus to

Determine delivery rate determination. Accordingly, it is necessary according to the invention that the liquid level or the position of the liquid front can be detected at three readout points of the metering tube. It is also necessary that after first performing steps (b) to (h) they are repeated, but the steps are not performed between the first read-out location and the second read-out location, but between the second read-out location and the third read-out location that a second delivery rate can be calculated. The use of two independent measuring sections makes it possible to obtain, during the conveying of the liquid to be metered and without recirculation, as described above, two independent values for the delivery rate which result from the correct functioning of the device according to the invention inventive method must be identical or at least almost identical; otherwise, it is particularly advantageous provided that the inventive method automatically interrupted and an error message, for example, to an operator, is output.

Likewise particularly preferably, it is possible to combine the different variants of the embodiments of the method according to the invention.

By means of the device according to the invention and using the method according to the invention, liquids can be used independently of their parameters, such as viscosity, density or temperature, as well as the amount to be metered Quantity be reliably and reproducibly dosed. Due to the simple calibration of the device according to the invention, the metering process is virtually independent of ambient parameters such as pressure or temperature. The device also allows quasi-continuously metering a virtually unlimited amount of liquid with high precision or with a very precisely adjusted delivery rate. Since the device comprises no moving parts for measuring the delivery rate except for the pumping device, this results in a special robustness of the entire device. Due to the good miniaturization of the detector principle, the device according to the invention is particularly suitable for use in correspondingly miniaturized systems, as used for example in the life sciences.

LIST OF FIGURES

Figure 1 shows a first embodiment of the inventive device 1 for exact dosing in a schematic view.

Figure 2 shows a second embodiment of the inventive device 1 for exact dosing in a schematic view.

Figure 3 shows a first embodiment of the method according to the invention for exact dosing in a view as a flow chart.

Figure 4 shows a second embodiment of the method according to the invention for exact dosing in a view as a flow chart.

figure description

1 shows a schematic representation of a first embodiment of the inventive device 1 for exact dosing in a schematic view.

A pumping device 2 conveys a liquid F to be dispensed from a reservoir 20. The pumping device 2 consists in the illustrated example of a unidirectionally conveying pump 2 ^* . The liquid to be metered F is replaced by a unspecified tubular device promoted in a metering tube 3. The geometry of the metering tube 3 is exactly predetermined. In particular, the inner cross section or inner diameter and the length of the metering tube 3 is exactly known so that the corresponding volume in the interior of the metering tube 3 can be calculated. The liquid F is limited during its passage through the metering tube at its front end by a corresponding liquid front 7, which is located in the illustrated example just before the first read-8. In a (not shown) Weiterfördern the liquid F leaves this outlet 3 ^{1 of} the metering tube 3 and drips into a metering vessel 21 into it.

Fig. 1 also shows a schematic representation of a first embodiment of a detector 4 according to the invention, which is designed as an electrical detector. This consists essentially of two projecting into the interior of the metering electrical conductors, which are shown in Fig. 1 by small arrows. At the same time, these arrows indicate the only read-out point 8 present in FIG. 1. A voltage source U is connected to one of the electrical conductors, and the other is connected to a drive unit 19. As soon as the liquid front 7 passes the read-out point 8, the electrical resistance changes there and thus the voltage applied there. This change can be detected by means of the drive unit 19 and thus serves to determine the position of the liquid front 7 according to the invention.

The drive unit 19 also comprises an input device 19 ', which is used to specify the device 1 according to the invention the desired amount of the liquid F to be metered. In addition, the drive unit 19 is connected to the pump device 2 by means of a further signal line (dash-dotted thin line).

Fig. 2 shows a schematic representation of a second further embodiment of the inventive device 1 for exact dosing.

A bi-directionally conveying pumping device 2 conveys a liquid F to be dispensed from a reservoir 20. The bidirectionally conveying pumping device 2 is in the illustrated example composed of two unidirectionally conveying pumps 2 '. These can be particularly advantageous in a common Enclosed housing, which is indicated by the framed dashed line. The liquid to be metered F is conveyed through a pipe-type device, not specified, into a metering tube 3. The geometry of the metering tube 3 is exactly predetermined. In particular, the inner cross section or inner diameter and the length of the metering tube 3, as well as the distance between the different readout points 8, 8 ', 8 "exactly predetermined so that the corresponding part volume can be calculated in the interior of the metering tube 3.

The liquid F is limited during its passage through the metering tube at its front end by a corresponding liquid front 7, which in the example shown between the second read-out 8 ¹ and the third

With a further conveying (not shown) of the liquid F leaves this de output 3 'of the metering tube 3 and drips into a metering vessel 21 into it.

Fig. 2 also shows another embodiment of a detector 4 according to the invention, which is designed as an optical detector 4 '. The optical detector 4 'initially comprises a light source 9. This emits, for example, white light in an illumination fiber 10, the first end 10A of the light source 9 faces. In the illustrated example, the illumination fiber 10 is divided into three individual fibers 15. Each of these three individual fibers 15 is in each case brought with its second end 10B to the metering tube 3, but each at a different point thereof, so that three spaced readout points 8, 8 ', 8 "result. (For reasons of clarity, only one the three existing second ends 10B of the individual fibers 15 of the illumination fiber 10 provided with the corresponding reference numeral.)

On the opposite side of the metering tube 3 are also three individual fibers 15, which can each receive the light emerging from the metering tube 3 with a first end 11A. The individual fibers 15 are then combined to form a common main fiber 14. Since this fiber composite serves to transmit the light in the direction of a device for collecting the light 13, it is also referred to as detector fiber 11. The light from the detector fiber 11 leaves it from its second end 11 B. The embodiment of the present embodiment of the device according to the invention shown in Figure 2 also shows three color filters 12, which are arranged between the respective second end of the illumination fiber 10B and the respective first end of the detector fiber 11A. According to the invention, these three color filters 12 each filter different wavelengths from the irradiated light, so that the originally white light, which is irradiated into the illumination fiber 10, is divided into three beams of different frequencies. These three different frequencies are collected beyond the metering tube 3 by the detector fiber 11 and summarized in the main fiber 14. FIG. 2 also shows that the individual fibers 15 of the illumination fiber 10 and the detector fiber 11 are aligned so as to form an optical path 18 which can be influenced both by the color filters 12 and the metering tube 3. This optical path 18 is symbolized by a bold dotted line in the area of the three readout points 8, 8 ', 8 "shown in Figure 2. In the illustrated embodiment of Figure 2, the means 13 for collecting the light has the capability of detecting the three from a second end 11A the detector fiber 11 emerging light beams of different frequencies to detect separately.

The means for collecting the light 13 is connected by a signal line, which is shown in the figure 2 by means of a thin dotted line, with a time measuring device 5, so this came in particular provide a start or stop signal. The time measuring device 5 is in turn linked to a drive unit 19. The drive unit 19 also comprises an input device 19 ', which is used to specify the device 1 according to the invention the desired amount of the liquid F to be metered. In addition, the drive unit 19 is connected by means of a further signal line to the bidirectionally conveying pump device 2. Not shown, but nevertheless present in the control unit 19 or directly associated therewith is a computing device with which the arithmetic operations necessary for carrying out the method according to the invention can be carried out.

It is clear that the detector 4,4 'according to the second embodiment of the present invention may also be advantageously provided in the first embodiment of the present invention. It will also be understood that in the first and second embodiments of the present invention, an appropriate mechanism for displacing and positioning the detector 4, 4 'described in the drawings for clarity may be provided for adjusting the predetermined metering volume.

Fig. 3 shows a first embodiment of the method according to the invention for exact dosing in a view as a flow chart which will become clear to the person skilled in the art from the above description.

Fig. 4 shows a schematic representation of the particularly advantageous second embodiment of the method according to the invention for exact dosing in a view as a flow chart. In a first step, the bidirectionally conveying pump device is switched on, and the delivery of the liquid to be metered from a reservoir begins. During delivery, a detector detects the presence of the liquid front of the liquid to be metered and transported at a first read-out location. As soon as the detector has detected the liquid front, it starts a time measuring device. Meanwhile, the pumping device remains switched on, and the liquid to be dispensed is conveyed further in the direction of the outlet of the metering tube. The detector now detects the presence of the liquid front at a second read-out location. As soon as the detector has detected the liquid front at the second read-out location, it stops the time-measuring device and the pump device.

From the known geometry of the metering tube and the distance between the first and the second readout point, the delivery rate can now be determined in conjunction with the delivery time, which was measured by the time measuring device.

On the basis of the also predetermined amount of liquid to be metered at that known conveying rate that conveying time can be calculated, which is necessary to promote the liquid to be metered to the end of the metering tube and then metered in the desired amount from this out. LIST OF REFERENCE NUMBERS

1 device for exact dosing

2 pumping device

2A bidirectionally pumping device

2 'unidirectional pump

3 dosing tube

3 "output

4 detector

4 'optical detector

5 time measuring device

6 valve

6 "external fluid connection

7 liquid front

8,8 ', 8 "readout

9 light source

10 lighting fiber

10A first end of the illumination fiber

10B second end of the illumination fiber

11 detector fiber

11A first end of the detector fiber

11B second end of the detector fiber

12 color filters

13 device for catching the light

14 main fiber

15 individual fibers

18 optical path

19 control unit

19 'input device

20 reservoir

21 dosing vessel

F to be dosed

F 'external fluid

Q delivery rate

Q 'second delivery rate X amount of liquid to be dispensed

Claims

claims

Device (1) for exact dosing of liquids, characterized in that the device comprises the following elements: a pump device (2); a metering tube (3) of known geometry; a detector (4) for detecting the liquid level; wherein the pumping device (2) is arranged so that the liquid to be metered (F) through the metering tube (3) is conveyed, and wherein the detector (4) is arranged so that the position of the liquid front (7) of the metered

Liquid (F) at at least one read-out point (8) of the metering tube (3) is detectable.

2. Device (1) according to claim 1, further comprising at least one valve (6), wherein at least one valve (6) is arranged so that the flow through the

Dosing (3) flowing liquid (F) can be interrupted, and instead an external fluid port (6 ') is switchable, and the pumping device (2) is also arranged downstream of the valve (6).

3. Device (1) according to claim 1, further comprising a time measuring device (5), wherein the time measuring device (5) from the detector (4) is controllable.

4. Apparatus according to claim 1, 2 or 3, characterized in that the

Detector (4) as an optical detector (4 ') is formed and a light source (9), at least one illumination fiber (10) for transmitting the light to the

Metering tube (3) and a detector fiber (11) for returning the light from the metering tube (3), and means for collecting the light (13), and the light source (9) is arranged so that the light in a first end ( 10A) of the illumination fiber (10) is einstrahlbar, and the illumination fiber (10) so arranged that a second end (10B) with a first end (11A) of the detector fiber (11) is in optical communication, and the metering tube (3) is arranged so that this optical connection can be influenced depending on the filling of the metering tube (3) is arranged, and the means for collecting the light (13) is arranged so that the light from a second end of the detector fiber (11 B) in the means for collecting the colored light (13) is einstrahlbar.

5. The device according to claim 4, characterized in that the optical detector (4) also color filter (12) for decomposing the white light into colored components, and by means of the means for collecting the light (13), the colored components are separately detectable.

6. Apparatus according to claim 4 or 5, characterized in that the illumination fiber (10) and / or the detector fiber (11) of the optical detector (4) each consist of a main fiber (14) which in places in several

Individual fibers (15) can be divided, and the regions of divided individual fibers (15) are each arranged on the dosing tube (3) such that the optical connection of the individual fibers (15) of both main fibers (14) can be influenced by the filling of the dosing tube (3), and possibly existing color filters (12) are arranged so that they are in the region of the divided individual fibers (15).

7. Device according to one of the preceding claims, characterized in that the pumping device (2) is designed as a bi-directionally conveying pumping device (2A) and consists of two counter-rotating, unidirectional pumps (2 ').

8. Apparatus according to claim 7, characterized in that the unidirectionally conveying pumps (2 ') are arranged serially.

9. Device according to one of the preceding claims, characterized in that the detector (4) is arranged so that the position of the liquid front (7) of the liquid to be metered (F) at three read-out points (8, 8 ', 8 ") of the metering tube (3) is detectable.

10. Device according to one of the preceding claims, characterized in that the device further comprises a drive unit (19) and / or a reservoir (20) and / or a Dosiergefäß (21), wherein the

Control unit (19) optionally inputs for signals of the time measuring device (5) and / or the detector (4), and an input device (19 ¹ ) for specifying the desired dosage, and also an output unit for controlling the pumping device (2) and a computing device for determining the activation duration for the pump device (2).

11. Method for exact dosing of liquids, wherein the following steps are carried out for dosing:

(7) Specifying the amount X of a liquid to be metered (F); (8) switching on a pump (2 ¹ ) and conveying the liquid to be metered (F) through a metering tube (3) in the direction of an outlet (3 ');

(9) continuously detecting the presence of the liquid front (7) of the liquid (F) to be metered in the metering tube (3) at a read-out point (8);

(10) turning off the unidirectional pump (2 ') as soon as the liquid front (7) reaches the readout position (8);

(11) switching over a valve (6), so that by means of the unidirectional pump (2 ') instead of the liquid to be metered (F), an external fluid (F') in the metering tube (3) can be conveyed;

(12) reconnecting the unidirectional pump (2 ') and conveying the external fluid (F') into the metering tube (3) so that it passes the liquid (F) to be metered through the metering tube (3) and out of the outlet (F) 3 ¹ ) of the metering tube (3) also pushes.

12. The method of claim 11 using the device according to any one of claims 1, 2 and 4 to 6.

13. Method for exact dosing of liquids, wherein the following steps are carried out for dosing:

(a) setting the amount X of a liquid to be dosed (F);

(b) switching on a pumping device (2) and conveying the liquid to be metered (F) through a metering tube (3) in the direction of an outlet (3 '); (c) continuously detecting the presence of the liquid front (7) of the liquid (F) to be metered in the metering tube (3) at a first read-out point (8);

(d) starting a time measuring device (5) as soon as the liquid front (7) reaches the first read-out point (8); (e) continuously detecting the presence of the liquid front (7) of the liquid (F) to be metered in the metering tube (3) at a second read-out point (8 ¹ );

(f) stopping the time measuring device (5) as soon as the liquid front (7) reaches the second read-out point (8 '); (g) turning off the pumping device (2);

(h) calculating the delivery rate Q of the fluid (F) from the quotient of the volume between the first and second read-out locations (8, 8 ') and the time measured by the time-measuring facility (5);

(i) calculating the time necessary to convey the predetermined amount of liquid (F);

(j) reconnecting the pumping device (2) and conveying the liquid to be metered (F) through the metering tube (3) over a period in which, while maintaining the previously calculated delivery rate Q both the filling volume between the second readout point (8 ') and Outlet (3 ') of the metering tube (3), as well as the volume of the amount X to be metered the liquid (F) is promoted.

14.A method according to claim 13, wherein subsequently the following steps are carried out: (k) operating the bidirectionally conveying pump device (2A) in the of

Exit (3 ') pointing away direction and return the metered liquid (F) in the metering tube (3);

(I) continuously detecting the liquid level in the metering tube (3) at a second read-out point (8 '); (m) turning off the bidirectional pumping device (2A) as soon as the

Liquid front (7) reaches the second read-out point (8 ').

15.A method according to claim 13 or 14, wherein for calibration, the liquid to be metered (F) is fed back in the direction of the output (3 ') away direction until the liquid front (7) reaches the first read-out point (8) or slightly exceeds , and then steps (b) to (h) are performed so as to obtain the actual delivery rate Q.

16.A method according to any one of claims 13 to 15, wherein the liquid level at three readout points (8, 8 ', 8 ") of the metering tube (3) is detectable, and wherein after a first performing steps (b) to (h ), but the steps are not performed between the first read-out point (8) and the second read-out point (8 ¹ ), but between the second read-out point (8 ') and the third read-out point (8 "), so that a second Delivery rate Q 'can be calculated.

17. The method according to any one of claims 13 to 16 using the apparatus according to any one of claims 1 and 3 to 10.