EP2760584A1

EP2760584A1 - Method and device for metering a working fluid

Info

Publication number: EP2760584A1
Application number: EP12769642.5A
Authority: EP
Inventors: Harald Gentischer; Daniel Biro; Jan Specht; Florian Clement; Maximilian Pospischil
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2011-09-30
Filing date: 2012-10-01
Publication date: 2014-08-06
Also published as: WO2013045711A1; DE102011114554A1

Abstract

The invention relates to a method for metering a working fluid, comprising the following method steps: A. providing the working fluid (1, 1 ') within a pressure-stable and dimensionally rigid pumping chamber (3, 3'); B. feeding a predetermined volume of an incompressible pumping fluid (6, 6') into the pumping chamber (3, 3') by means of a metering pump (5), wherein, at an interface in the pumping chamber (3, 3") between the pumping fluid (6, 6') and the working fluid, which interface divides the pumping chamber (3, 3') into a pumping fluid region and a working fluid region, I. a flexible diaphragm forming the interface is arranged in the pumping chamber (3, 3'), or II. the pumping fluid (6, 6') is directly adjacent to the working fluid at the interface, and the working fluid (1, 1') is dispensed from at least one working fluid opening (4, 4') in the pumping chamber (3, 3') by the working fluid (1, 1') being displaced in the pumping chamber (3, 3') by the pumping fluid (6, 6') being fed in. The invention furthermore relates to a device for metering a working fluid.

Description

Method and device for dosing a working fluid

description

The invention relates to a device and a method for dosing a Arbeitfiuids.

In a large number of technical applications, it is necessary to dispense or to supply fluids from a reservoir in defined individual quantities or with a defined volume flow with a predetermined dosing accuracy value.

Usually, fluids are delivered during dosing with the aid of pumps, such as diaphragm pumps, gear pumps, gerotor pumps, peristaltic pumps, peristaltic pumps or piston pumps. Often systems are also used in which the fluid to be metered is provided in a plastic cartridge and is pressed directly, for example by compressed air from the cartridge or by a mechanically driven piston exerts a force on the fluid in the cartridge. Finally, fluidic conveying devices which operate according to the extruder or screw conveyor principle are also known.

Basically, the challenge with dosing is not only to deliver and dispense a fluid, but also to control the delivered and dispensed amount with the accuracy needed for the particular application. If the application permits it, then gravimetric measuring methods are used to measure the quantity delivered. In this case, the mass of the dispensed fluid is determined at the issuing point during the dosing with a weighing device. In this case, only small demands are placed on the conveying accuracy of the fluidic conveying device, since the measuring accuracy is limited only by the accuracy of the weighing device.

If, due to the application, it is not possible to use a gravimetric measuring method to control the dosing process, then one uses a volumetric metric method. In favorable cases, flow meters can be used. In other cases, even the knowledge about the displacement volume of the fluidic conveying device is sufficient in dependence on the relative driving position of the displacing parts of the fluid conveying device in order to determine the conveyed quantity of the fluid. For example, in systems where the fluid is pushed directly out of a cartridge, the delivered amount of media may be determined by multiplying the piston area by the offset of the piston position. In contrast, when the fluid in these devices is displaced with the aid of compressed air, 10 usually time / pressure controlled control systems are used. In this case, one forms the integral of the pressure curve in the cartridge over time in conjunction with a mathematical model of the flow behavior of the respective fluid in the cartridge and in all connection and connection elements to the exit point.

15 While a large number of fluids can be dosed excellently and with high dosing accuracy values, there are also fluids with which this is only possible to a limited extent. If, for example, fluids which have a very high viscosity are to be metered, membrane pumps or peristaltic pumps, inter alia, are excreted in order to convey them, because these pumps can not exceed a certain delivery pressure. If fluids are dosed in which particles are embedded from a solid, so pumps, such as gear and gerotor pumps, and piston and screw pumps can be used only if there is sufficient mechanical clearance between the moving parts of the fluidic conveying device 25. The mechanical clearance is necessary in order to prevent parts of the dosing pump from becoming jammed by the particles embedded in the fluid or to prevent the stored particles from being deformed by moving parts of the fluidic conveying device. However, the game results in that the achievable pressure is limited, thus only fluids can promote up to a bestimmst) th viscosity. As much as this increases the slippage of the fluidic delivery device, one loses the ability to determine the amount delivered via the displacement volume of the device. In addition, the abrasive property of the stored particles leads to the progressive wear of all parts of the fluidic conveying device, which come into contact with the flowing medium. An undesirable consequence is in addition the wear of the device also the fact that the medium is contaminated by the particles removed by parts of the device.

There are also difficulties with other volumetric measuring and dosing methods. For example, in time- / pressure-controlled systems, the flow behavior of filled fluids can only be described to a certain degree using mathematical models, which limits the dosing accuracy values to be achieved. Flowmeters can generally only be used at a certain flow rate. In this case, the measurement accuracy is limited depending on the method used and depending on the type of fluid to be dosed.

Another form of complication are fluids with aggressive chemical or harmful properties. If such substances are promoted, only materials resistant to the respective substances can be used for the parts of the fluidic delivery device and for supply and discharge lines. This may result in restrictions on the achievable operating parameters. In addition, the expense of cleaning the device can be a high level and, as well as the provision of such fluids, pose a hazard to operators.

All these phenomena that occur in the interaction of difficult-to-handle media with the respective metering systems have led to the use of time / pressure-controlled cartridge metering systems according to the current state of the art for metering the fluids mentioned, in which the fluids are provided in cartridges and therefore not or only to a small extent with the metering come into contact. On the one hand, this has the advantage that the fluids can not interact with parts of the fluidic delivery device. On the other hand, the cleaning effort is limited to replacing the cartridge and, if necessary, the attached nozzle. The difficulty with this system, however, is that for metered delivery of the fluids a mathematical model must be created, which describes the flow behavior of the respective fluid in the device to the outlet opening in dependence on a variety of parameters and external influences. For filled, thixotropic fluids, it is particularly difficult to predict the flow properties because they exhibit non-Newtonian behavior, ie, the flow properties change in particular depending on the pressure and on the respective flow velocity at each individual point of the conveying path. External influences, such as temperature and air pressure, must also be taken into account from a specific dosing accuracy value. Even with the slightest changes to the system or the external conditions, for example when a different nozzle is used, the mathematical model has to be adapted in a complex manner. Particularly unfavorable is the fact that separate, extremely complex Theological investigations must be carried out for each fluid used to determine the parameters necessary for operation for calculating the flow behavior. Last but not least, the difficult-to-calculate expansion behavior of the cartridge as a function of the pressure in the cartridge and of the ambient pressure must also be included in the calculation. Even if this is successful, the elongation of the cartridge in each Einzeldosiervorgang leads to a time lag between the time of pressure build-up and reaching the yield point of the fluid and thus to a delay of the fluid output, whereby the number of Einzeldosiervorgänge per unit time is severely limited. Slightly better accuracy values can be achieved if the fluid-displacing force is not introduced by means of compressed air but with a mechanically driven piston. Limiting factors in this variant, however, continue to be the expansion behavior of the cartridge and the positioning accuracy of the piston. Some attempts are made to reduce the expansion of the cartridge under pressure by partially encapsulating the cartridge by mechanical means. However, these forms of mechanical encapsulation are not completely positive with respect to the cartridges, so stretching can not be completely prevented. Even in favorable cases, in which fluids with rather low viscosity and with Newtonian properties are used, no comparably high dosing accuracy values can be achieved for the reasons mentioned with time / pressure-controlled cartridge dosing systems, as in the case of rigid fluidic conveying devices which work according to the volume displacement principle ,

A device for dosing liquids comprising an optical fluid measuring device is disclosed in DE 10 2008 016 513 A1. A device for dosing small amounts of liquid with dispensing from a Suction volume is disclosed in DE 197 42 005 A1, a volumetric working

Dosing valve in EP 1 864 721 A1,.

The present invention has for its object to provide a method and apparatus for metering a working fluid to output working fluids with a wide range of material parameters, in particular viscosities, with improved dosing accuracy. In particular, the method according to the invention and the device according to the invention are intended to improve the metering of pasty working fluids and / or working fluids provided with solid particles with regard to the metering accuracy.

This object is achieved by a method for dosing a working fluid according to claim 1 and by a device for dosing a working fluid according to claim 8. Preferably embodiments of the method according to the invention can be found in the claims 2-7. Preferably embodiments of the device according to the invention can be found in the claims 6 - 1 8. A use according to the invention can be found in claim 19. Herewith the wording of all claims is explicitly included by reference in the description.

The inventive method is preferably designed for implementation by means of the device according to the invention and / or a preferred embodiment thereof. The device according to the invention is preferably designed for carrying out the method according to the invention and / or a preferred embodiment thereof.

The invention is based on the Applicant's finding that, although pumps are known for high-precision metering, such high-precision metering pumps achieve the desired high accuracy only with liquids of particular parameters, in particular liquids in a certain viscosity range. When using such pumps for working fluids with different physical parameters, in particular different viscosities, thus fluctuates the dosing accuracy. In addition, highly viscous working fluids, such as pastes, are often not suitable for use with high accuracy dosing pumps. A first aspect of the invention therefore consists in the inventive method and the invention Device to promote a defined volume of an incompressible pumping fluid by means of a metering pump, which pumping fluid in turn leads by displacement to a synchronous output of the working fluid: The inventive method for metering a working fluid comprises the following method steps:

In a method step A, a working fluid is provided within a pressure-stable and dimensionally stable pumping chamber. Pressure-stable here and below means that the pumping chamber is on the one hand dimensionally stable with respect to the intrinsic pressure occurring in the pumping chamber during use and, on the other hand, dimensionally stable with respect to the ambient pressure acting on the pumping chamber. In this case, dimensionally stable means in this case and in the following that no or at least essentially none or a negligible deformation of the components through which fluid flows in the region of the required metering accuracy takes place due to the action of pressure.

In a method step A, an incompressible feeding takes place

Pumping fluid by means of a metering pump in the pumping chamber, wherein in the pumping chamber at an interface between the pumping fluid and working fluid, which

The pump chamber is subdivided into a pump fluid region and a working fluid region, in a first variant I a flexible membrane forming the interface is arranged in the pumping chamber or in a second variant I I the pumping fluid directly adjoins the working fluid at the interface.

Furthermore, in method step B, the working fluid is dispensed from at least one working fluid opening of the pumping chamber, in that the working fluid in the pumping chamber is displaced by supplying the pumping fluid.

The inventive method thus differs in at least two essential aspects of the prior art method for dosing an incompressible working fluid, on the one hand a decoupling between metering pump and working fluid takes place such that by means of the metering pump only an incompressible pumping fluid is promoted and on the other hand in terms of the operation of a dosing a complete mechanical coupling is achieved between the pumping fluid and Arbeitsfiuid by a flexible membrane (variant I) is disposed at an interface in the pumping chamber or the pumping fluid directly adjacent to the Arbeitsfiuid {variant II), this results in particular the advantages that pumping fluid and metering pump with respect to a maximum possible Metering accuracy can be optimized. In particular, the physical properties of the pumping fluid can be chosen such that the greatest possible metering accuracy is achieved by means of the metering pump used. In addition, the dosing accuracy is substantially due to the dosing accuracy, by which the metering pump promotes the pumping fluid, due, so that the dosing accuracy achieved is largely independent of the Arbeitsfiuid used. Moreover, the interface between working fluid and pumping fluid is either formed by a flexible membrane or the pumping fluid immediately adjoins the working fluid. As a result, a significantly larger range of working fluids can be metered with higher accuracy, compared to previously known dosing methods. Particularly in the case of previously known methods, in which the working fluid is forced out of the cylinder by means of a piston within a cylinder, errors typically occur on sealing elements between piston and cylinder, in particular when using working fluids which comprise solid particles, in particular the solid particles Such sources of error are eliminated in the method according to the invention, since in variant I, a flexible membrane is used, which thus by displacement and / or expansion displacement of the working fluid within the Pumping chamber allows, without a relative movement between the flexible membrane and a wall of the pumping chamber - as is done between piston and cylinder - is necessary. In variant II, the pumping fluid directly adjoins the Arbeitsfiuid, so there are no elements that could lead to the aforementioned problems.

The invention is based in particular on the recognition of the Applicant that the highest possible dosing accuracy values can be achieved if the dosing quantity does not have to be measured either directly or indirectly, but in which the desired volume to be dispensed can be deliberately and reliably pre-determined with a suitable device. This is realized with the method according to the invention. The device according to the invention for metering a working fluid comprises a pressure-stable and dimensionally stable pumping chamber and a metering pump for conveying an incompressible fluid

Pumping fluid. The metering pump is connected via a fluid line with a pumping fluid opening of the pumping chamber in order to supply and / or discharge pumping fluid and the pumping chamber has at least one working fluid opening in order to supply and / or remove a working fluid.

The pumping chamber is designed in such a way that, in use, an interface between the pumping fluid and the working fluid is formed in the pumping chamber, which interface divides the pumping chamber into a pumping fluid region in which the pumping fluid opening m opens and a working fluid region in which the working fluid orifice opens, wherein in a variant I, an interface forming the flexible membrane is arranged in the pumping chamber or in a variant II, the pumping fluid at the interface directly adjacent to the working fluid. The device according to the invention also has the aforementioned advantages of the method according to the invention.

In a preferred embodiment, the pumping chamber for receiving a working fluid-containing cartridge is formed with an at least partially flexible designed cartridge wall. In this preferred embodiment, therefore, at least the flexibly formed part of the cartridge wall forms the flexible membrane according to variant I. In this preferred embodiment, therefore, the working fluid can be provided in a simple manner according to method step A by arranging the cartridge in the pumping chamber. Preferably, the pumping chamber has seals and / or a closure system for fluid-tight application of the cartridge walls to walls of the pumping chamber, so that after arranging the cartridge in the pumping chamber, the area not executed by the cartridge in the pumping chamber is fluid-tight and only via the pumping fluid opening a volume exchange is possible. In another preferred embodiment according to variant I, the flexible membrane is arranged in the pumping chamber and fluid-tightly connected to one or more walls of the pumping chamber. Thus, the distribution of the pumping chamber in the pumping fluid region and working fluid region is given by the membrane and the volume changes of these regions, ie for example enlargement of the volume of the pumping fluid region and at the same time reduction of the volume of the working fluid region for dispensing working fluid, take place by deformation and / or stretching of the membrane , It is within the scope of the invention that the membrane is formed after a bubble, which bubble is arranged within the pumping chamber and only has an opening which encloses the pumping fluid opening or in another preferred embodiment, the working fluid opening. In the first case, pump fluid can thus be fed into the bladder opening and thus into the bladder via the pump fluid opening and can be discharged from the bladder. In the second case, conversely, working fluid can be introduced into the bladder through the bladder opening via the working fluid opening or out of the bladder.

Investigations by the applicant further showed that the metering accuracy of prior art metering systems is surprisingly affected to a degree not to be neglected by fluctuations in the ambient pressure. In a preferred embodiment, therefore, at least the flow path between the metering pump and the pumping chamber is pressure-stable with respect to ambient pressure acting on the device. In particular, it is advantageous that the metering pump is connected in a fluid-conducting manner to the pumping chamber via lines which are stable in terms of external pressure and internal pressure and are dimensionally stable. As a result, a reduction in the dosing accuracy is wholly or at least essentially excluded, since the system dosing pump, pumping chamber and fluid line between dosing pump and pumping chamber is not affected by a changing ambient pressure and in particular the respective internal volume does not change due to a changing ambient pressure. A rigid design of the leads also causes a maintenance of the mechanical coupling between the pumping fluid and working fluid in the relevant area for controlling the Dosiermenge area of the system and thus an independence of the dosing of fluctuations in the ambient pressure. It is therefore particularly advantageous for pumping fluid and working fluid to be enclosed in a closed system in the form of a pressure-stable and dimensionally stable housing from the point of presetting of the metering volume up to the point of discharge of the working fluid, which at most with the ambient pressure via the dispensing opening during the metering process the pumping chamber or a cartridge located in the pumping chamber is in pressure communication.

Due to the pressure-stable and dimensionally stable design of the pumping chamber and the connecting elements to the metering pump and due to the fact that the pumping fluid and working fluid in the area between the metering pump and the working fluid opening share the same volume, the volume flowing into the pumping chamber corresponds at all times to the effluent at the working fluid openings Volume.

Investigations by the applicant further showed that, surprisingly, the metering accuracy is frequently impaired by a "run-on", whereby after completion of the actual metering operation and in particular stoppage of the metering pump, working fluid emerges from the working fluid opening Device to be avoided or at least significantly reduced according to the invention:

Preferably, in a method step C after method step B, the pressure of the pumping chamber is equalized to an ambient pressure. For this purpose, a relief valve is opened, which is pressure-compensating connected to an environment and the pumping fluid region and / or the working fluid region of the pumping chamber. In this preferred embodiment, therefore, after the desired amount of working fluid has been dispensed directly, a pressure relief in the pumping chamber takes place so that afterrunning is prevented in a simple and efficient manner. For this purpose, the relief valve may be formed as a vent valve, as described below in an advantageous manner. Likewise, it is within the scope of the invention that, although the relief valve establishes a connection with the environment in the open state for pressure equalization, it does not produce a fluid-conducting connection. For example, a flexible surge tank can be provided which can be connected via the relief valve. Til fluidly connected to the pumping fluid region and / or the working fluid region of the pumping chamber, so that when the relief valve is open

Preferably, the relief valve is connected to the working fluid portion of the pumping chamber to efficiently provide pressure equalization with the environment upon completion of the dosing operation.

The aforesaid preferred embodiment comprising a relief valve is particularly useful in dynamic printing operations, i. H. Printing processes in which a plurality of Dosiermengen, in particular in a short cycle must be delivered, advantageous. Particularly when using the method according to the invention and the device according to the invention for applying working fluid to a solar cell in the production of photovoltaic solar cells highly dynamic metering operations are required, so that in particular in such an application, the previously described advantageous embodiment comprising a relief valve considerable advantages in terms Dosing accuracy offers.

In a further development of the advantageous embodiment described above, the relief valve is closed before method step B, preferably before method steps A and B, so that regardless of the ambient pressure, the supply of a predetermined volume of the pumping fluid or on the provision of the working fluid. Applicant's investigations have furthermore shown that the dosing accuracy can still be impaired by an output delay in process step B. In practical application cases, the feeding of the predetermined volume of the incompressible pumping fluid in process step B leads to an output of the working fluid from the working fluid opening only with a time delay. This may be due to the fact that no complete venting has taken place or that at other places there are at least slightly compressible elements or volumes which thus result in no ideal pressure-stable system of incompressible liquids being present. This disadvantage can be counteracted by the fact that in method step B, prior to discharge of the fluid, the working fluid region is charged with a pre-pressure which is in the range from 50% to 95%, preferably 85% to 95%. Preferably, about 90% of the pressure necessary for dispensing working fluid is present. In this preferred embodiment, a pre-pressure in the working fluid region of the pumping chamber is thus already generated before the actual dosing, but which form is below a pressure threshold for the output of working fluid. As a result, a compression of any compressible volumes or other pressure-receiving elements is already achieved when building up the form, so that at the start of the actual dosing no or a significantly reduced delay is achieved until the output of the working fluid and thereby the dosing accuracy is further increased. The application of a pre-pressure is preferably also via the metering pump and supplying pumping fluid in the pumping fluid region of the pumping chamber. In particular, pressure sensors are preferably provided in the pumping chamber, preferably in the pumping fluid region of the pumping chamber, in order to build up a predetermined admission pressure in the pumping chamber by means of a likewise preferably provided control unit.

The pre-pressure described above can be generated by means of the metering pump. It is particularly advantageous, the admission pressure exclusively by means of a suction side of the pump arranged pressure source, in particular a one

In particular, it is advantageous that the inlet pressure on the suction side of the metering pump is at least 90% of the pressure required to dispense working fluid. Since a pump is typically not absolutely pressure-tight even at a standstill, the pre-applied pressure on the suction side transmits at least attenuated even when the pump is stationary pressure on the pumping fluid and thus the pumping chamber and the working fluid in the working fluid.

Preferably, the pumping chamber has a venting valve fluidly connected to the pumping fluid region. This makes it possible in particular to fill in a preferred embodiment of the method according to the invention between method step A and B not occupied by the working fluid volume of the pumping chamber by means of the metering pump with pumping fluid, optionally in the pumping chamber existing gas is removed via the vent valve from the pumping chamber , Subsequently, the vent valve can be closed so that there is no interaction between the ambient pressure and the pumping chamber. Preferably, in the device according to the invention, the metering pump is connected in a fluid-conducting manner, on the one hand, to the pumping fluid filling of the pumping chamber and, on the other hand, to a pumping fluid reservoir. In particular, it is advantageous that the pumping fluid reservoir is pressure-stable in relation to the ambient pressure or designed to be closed in a pressure-stable manner. By means of the pumping fluid reservoir, pumping fluid can be provided in a simple manner for introduction into the pumping chamber and, when the pumping chamber is emptied, the pumping fluid pumped off from the pumping chamber can be stored again in the pumping fluid reservoir. The pressure-stable design leads to an additional increase in the dosing accuracy, as in this preferred embodiment, the suction side of the metering pump {when pumping pump fluid into the pumping chamber) no or at least substantially no pressure fluctuations in a change in ambient pressure, or by the pressure fluctuations that resulting from the changes in the level in the pumping fluid reservoir, occur.

In this case, it is particularly advantageous for a compressed gas source to be connected in a fluid-conducting manner to the pump fluid reservoir. In this way, a constant pressure in the pumping fluid reservoir can be maintained even when removing pumping fluid by means of the compressed gas, so that in addition the pressure conditions are kept constant on the suction side of the metering pump and thus additionally the metering accuracy is increased.

A further increase in the dosing accuracy is achieved in a preferred embodiment in that a pressure control valve is arranged between the pump fluid reservoir and dosing pump, so that the pressure applied to the dosing pump can be regulated to a constant value by means of the pressure control valve on the suction side in order to increase the dosing accuracy even further. Accordingly, in a preferred embodiment of the method according to the invention in process step B of the metering pump suction fluid pump fluid from a pump fluid reservoir supplied, which pump fluid reservoir is preferably pressure stable to the ambient pressure is completed. In particular, it is advantageous that gas is added to the pumping fluid reservoir by means of a compressed gas source in order to maintain a predetermined pressure in the pumping fluid reservoir. leads. As a result, the dosing accuracy is increased as described above.

In order to provide working fluid in the pressure-stable and dimensionally stable chamber in the working fluid region, it is within the scope of the invention, as described above, to arrange a cartridge containing working fluid in the pumping chamber.

In another preferred embodiment of the method according to the invention in step A pumping fluid is removed by means of the metering pump from the pumping chamber to generate a negative pressure in the pumping chamber and to introduce working fluid from a working fluid reservoir into the pumping chamber. In this way, therefore, the metering pump can be additionally used to suck working fluid into the pumping chamber to provide the working fluid for a subsequent metering in the pumping chamber available.

In this case, it is within the scope of the invention that for filling the working fluid area of the pumping chamber with working fluid, a fluid line which is connected to a working fluid reservoir is connected to the working fluid opening and after provision of the working fluid in the pumping chamber this fluid line is removed again.

In a preferred embodiment of the device according to the invention, a working fluid reservoir is provided which is conductively connected to the working fluid region of the pumping chamber. In this case, it is particularly advantageous for the working fluid reservoir to be fiuidleitend connected thereto via a second opening of the pumping chamber, so that this opening is thus formed as Arbeitsfluidzu- opening to direct working fluid from the working fluid reservoir into the pumping chamber and continue the pumping chamber having the aforementioned working fluid opening which is thus formed in this preferred embodiment as Arbeitsfluidausgabeöffnung. In this case, it is particularly advantageous to provide for the venting of the pumping chamber in the flow path between the working fluid reservoir and the pumping chamber and / or on the working fluid discharge opening optionally closable valves to close the working fluid dispensing opening when filling the working fluid area of the pumping chamber and to open the flow path between working fluid reservoir and pumping chamber , When emptying the working fluid area of the pumping chamber, that is at output of working fluid, inversely, the flow path between the working fluid reservoir and the pumping chamber is closed and the working fluid discharge port is opened. The working fluid reservoir is preferably pressure-stable with respect to the ambient pressure and is dimensionally stable or at least pressure-resistant and can be closed in a dimensionally stable manner. This ensures that the working fluid reservoir can be acted upon by an overpressure in order to prevent the pumping chamber from being filled with a vacuum at the discharge opening of the pumping chamber, thus eliminating the risk of transferring ambient air or particles from the environment suck in the delivery port into the pumping chamber.

Preferably, a compressed gas source is provided, which is fluid-conductively connected to the working fluid reservoir. In this way, it is additionally prevented that, when the pumping chamber is filled with working fluid, ambient air or particles from the environment are sucked into the pumping chamber via the dispensing opening. The metering pump can be designed in the manner of known per se known conveying devices for incompressible pump fluids and it is basically at the discretion of the person skilled in the art to use any conveying device as a metering pump. In particular, no continuous continuous operation is necessary, that is, a pumping device, which consists of a filled with pump fluid cylinder-piston unit, the piston by means of further hyd raulischer components and / or mechanical com ponents is movable, can also be used as a metering pump.

In particular, however, the use of conveying systems with a high degree of tightness and thus a particularly low slip in terms of

Pumping fluids advantageous. Thus, the metering pump is preferably designed as a piston, gear or tooth ring pum pe. The individual components of the dosing pump used preferably have a sufficiently high degree of precision in interaction, so that elastic seals can be dispensed with and the dosing accuracy is increased hereby. The pumping fluid preferably has Newtonian flow properties. Preferably, the viscosity of the pumping fluid is in the range between 5000 mPas and 40,000 mPas. In this area, according to experience, suitable metering pumps have the greatest tightness or the lowest slip.

It is within the scope of the invention to use gaseous working fluids. However, a particularly high accuracy of the dispensed volume of the working fluid results in particular when using incompressible working fluids and in this case preferably from a liquid as the working fluid.

A further increase in the dosing accuracy can be achieved in the following preferred embodiment:

In the flow path between metering pump and Pumpfluidoffnung the pumping chamber, a hydraulic cylinder is preferably arranged so that a first volume of a first hydraulic cylinder with the Pumpfluidoffnung the Pumpkamme and a first volume of the second hydraulic cylinder is fluidly connected to the metering pump. The pistons of the two hydraulic cylinders are mechanically coupled such that a volume change in the first volume of the second cylinder due to the mechanical coupling of the pistons results in a volume change in the first volume of the second hydraulic cylinder. It is essential that the piston cross-sectional area of the second hydraulic cylinder is greater than the piston cross-sectional area of the first hydraulic cylinder. As a result, a volumetric gear ratio is thus achieved by means of the metering pump, a first volume is conveyed, which leads to the introduction of a second volume of pumping fluid into the pumping chamber, wherein the first volume is greater than the second volume. orzugswelse here is a gear ratio of at least 1: 2. The transmission ratio is preferably selected according to the required dosing accuracy.

As a result, a further increase in the metering accuracy is achieved, since in particular small volumes can not be metered with high accuracy by means of a metering pump. Due to the volumetric translations by means of the two hydraulic cylinders with different piston cross-sectional area, a pumping fluid can thus be conveyed into the pumping chamber, by contrast, a larger volume by means of the metering pump for introducing a predetermined volume. Preferably, the two hydraulic pistons can be bridged by means of a bypass line, so that optionally there is a direct fluid-conducting connection between metering pump and pumping chamber, in particular in order to fill the pumping fluid region of the pumping chamber with pumping fluid. A particularly simple embodiment of this selectively switchable bypass fluid line is obtained by a valve is arranged in the bypass fluid line and in a fluid idleitung between metering pump and second hydraulic cylinder also a valve is arranged. The flow paths are preferably configured such that - when pumping fluid is pumped into the pumping chamber - a flow path branching is formed on the pressure side of the metering pump, whereby one branch via an optionally closable valve as a bypass line leads directly to the backfilling of the pumping chamber and the other branch via a second optionally closable valve opens into the first volume of the second cylinder-piston unit.

The device according to the invention and the method according to the invention are fundamentally suitable for applications in which a highly accurate metering of a working fluid is necessary. In particular, owing to the decoupling of the pumping fluid delivered by the metering pump and the working fluid used for the field of application, it is particularly suitable for applications in which highly viscous working fluids are used, in particular working fluids having a high viscosity and / or fields of application where pasty working fluids are used and / or applications using solid state fluids and / or applications using non-Newtonian working fluids and / or aggressive or noxious chemical properties.

The device according to the invention and / or the method according to the invention are therefore preferably designed for the use of and / or are preferably used with

a non-Newtonian fluid as the working fluid, preferably one with

Solid particles filled fluid, in particular with metal particles and / or ceramic particles (eg glass frit) filled fluid;

and or - A fluid having a viscosity greater than 100 mPas, preferably greater

1000 mPas, preferably greater than 10,000 mPas, more preferably greater than 100,000 mPas.

A preferred application relates to the production of photovoltaic solar cells: Here, process steps are often necessary in which a paste-like working fluid to be applied in one or more parallel tracks on a semiconductor substrate. The pasty working fluid may be, for example, a metal particle-containing paste having a viscosity of bi to 500,000 mPas for producing a metallic contacting structure. Likewise, the use of a dopant-containing paste for generating doping regions in the semiconductor substrate is possible.

The inventive method and the device according to the invention are suitable for incompressible fluids. In particular, however, the method according to the invention and the device according to the invention are also suitable for compressible fluids, in particular compressible gases, due to the high dosing accuracy. Further preferred fields of application are:

Dispensing of adhesives, conductive adhesives and solder pastes in the manufacture of electronic circuits

Dosing applications in the pharmaceutical industry

Dosing applications in the food industry

Dosing applications in medical technology

Dosing applications in the chemical industry

Generally dosing applications where the working fluid must never be contaminated

Generally dosing applications where there is a risk of the working fluid for humans or the environment

Generally high-precision volumetric dosing of gases

Generally high-precision volumetric dosing of non-Newtonian

fluids Further preferred features and embodiments of the method according to the invention and of the device according to the invention are explained below on the basis of exemplary embodiments and the figures. 1 shows a first exemplary embodiment of a device according to the invention, in which a working fluid region of a pumping chamber is filled via a working fluid opening;

2 shows a second embodiment of a device according to the invention, in which working fluid from a working fluid area via a

Working fluid output opening can be dispensed and working fluid from a working fluid reservoir can be fed into the pumping chamber via a separate working fluid supply opening; Figure 3 shows a third embodiment according to the structure of Figure 1, which additionally comprises a volumetric translation device.

Figure 4 shows a fourth embodiment of a device according to the invention according to the second embodiment of Figure 2, which additionally has a volumetric translation device.

In FIGS. 1-4, the same reference numerals designate the same or equivalent elements. FIG. 1 shows a first exemplary embodiment of a device A for metering a working fluid 1. With reference to the apparatus of Figure 1, a first embodiment of a method according to the invention will be further described.

The working fluid 1 is located in a cartridge 2. The cartridge 2 is arranged in a pumping chamber 3 in a method step A. The cartridge 2 has a working fluid opening 4 and, after insertion into the pumping chamber 3 at the edges of the working fluid opening 4, is connected in a fluid-tight manner to an edge of the pumping chamber 3 surrounding the working fluid opening 4. In FIGS. 1 to 4 and the exemplary embodiments described here, the working fluid 1 is in each case designed as a printing paste provided with metal particles. forms. The printing paste is applied to a semiconductor substrate, preferably a preliminary stage in the production process of a photovoltaic solar cell, to form a metallic contacting structure. The enclosed by the cartridge 2 volume, which is filled with working fluid, thus represents the working fluid in the pumping chamber 3. A metering pump 5, which is designed for example as a gerotor pump is connected via a pressure-stable and dimensionally stable fluid line 8 with a pumping fluid opening of the pumping chamber 3 , The metering pump 5 is furthermore connected to a pump fluid reservoir 9 via a pressure-stable fluid line.

After the cartridge 2 has been introduced into the pumping chamber, pumping fluid 6 can thus be conveyed out of the pumping fluid reservoir 9 into a pumping fluid region of the pumping chamber 3 by means of the metering pump 5. If necessary, in the

Pump fluid portion of the pumping chamber 3 located gas is discharged via a vent valve 7, wherein a collecting container 1 5 is provided to catch possibly exiting via the vent valve pumping fluid 6.

As soon as the pumping fluid region of the pumping chamber 3 is completely filled with pumping fluid 6, the venting valve 7 is closed.

Subsequently, in a method step B, a predetermined amount of pumping fluid 6 is supplied to the pumping chamber 3 by means of the metering pump 5. Since the pumping fluid is incompressible and since both the pumping fluid and the working fluid share the volume contained in the pressure-stable and dimensionally stable pumping chamber, the volume of pumping fluid 6 supplied to the pumping chamber corresponds to the volume of working fluid 1 dispensed at the working fluid port 4.

The working fluid 1 is thus dispensed, since in the pumping chamber 3 by supplying pumping fluid 6, the volume of the pumped fluid area increases and correspondingly decreases due to displacement of the volume of the working fluid area. The outer wall of the cartridge 2 is designed to be flexible and thus forms the flexible membrane between the pumping fluid region and the working fluid region. During the dispensing operation of working fluid 1, a pressure P is thus discharged into the pumping chamber 3 without any significant delay by supplying pumping fluid 6. built, which leads to a reduction of the volume of the working fluid in the pumping chamber 3.

The high dosing accuracy is thus on the one hand by the design of the metering pump as a high-precision metering pump in training, for example, as a toothed ring pump, which steals no elastic seals, guaranteed. Furthermore, at least the elements arranged in the region C are in each case pressure-stable and dimensionally stable, so that an internal volume enclosed by these elements does not change either with a change in the ambient pressure B or by the overpressure in the interior.

The metering pump 5 is on the suction side (in terms of the direction of flow when supplying pumping fluid 6 to the pumping chamber 3) via a fluid line with a

Pumpfluidreservoir 9 connected. The fluid line between Pumpfluidreservoir 9 and metering pump 5 is also formed pressure stable to further increase the dosing accuracy. A pressure-stable design is sufficient at this point, since before the pump only the constant pressure is important and not a constant volume. A dimensionally stable design of this fluid line is therefore not absolutely necessary.

Furthermore, in this line, a pressure regulating valve 1 1 is provided, by means of which the suction side of the metering pump (conveying pumping fluid into the pumping chamber 3) applied pressure is predetermined, so achieved due to this suction side constantly applied to the metering pump during the delivery pressure, a further increase in dosing accuracy becomes.

In addition, the dosing accuracy is increased by the pumping fluid reservoir 9 formed pressure stable and pressure-sealed from the environment. Upon removal of pumping fluid 6 from the pumping fluid reservoir 9, a constant gas pressure is generated in the region of the pumping fluid reservoir 9 not occupied by the pumping fluid by means of a compressed gas source 10 via a fluid line which has an optionally closable valve 13, so that additionally a pressure fluctuation on the suction side of the metering pump 3 is avoided. If the cartridge 2 is to be exchanged, in particular if the cartridge is empty, pumping fluid is pumped out of the pumping chamber 3 by means of the metering pump 5 into the pumping fluid reservoir 9 by conveying inversion. In this case, the valve 13 is closed and a vent valve 14 is opened.

In a further exemplary embodiment of the method according to the invention, the dosing accuracy is increased, in particular in dynamic metering processes, by opening the venting valve 7 after method step B in a method step C so that pressure equalization between the pumping fluid region 6 'and the environment (via the collecting container open to the environment 15) is produced and thus an immediate termination of the output of working fluid from the working fluid opening 4 is achieved. The bleeder valve 7 thus also serves as a relief valve in this preferred embodiment. Before the next dosing operation, the venting relief valve 7 is closed again in order to allow a pressure build-up in the pumping chamber 3 by means of the dosing pump 5.

In a further embodiment of the method according to the invention, a pre-pressure in the pumping chamber 3 is constructed prior to the dosing, which corresponds to about 90% of the pressure at the working fluid exiting the working fluid opening 4. For this purpose, the pumping chamber 3 has a pressure sensor (not shown) in the working fluid region, which is connected to a control unit (also not shown). The control unit controls the dosing pump 5 depending on the measuring signals of the pressure sensor such that before starting the actual dosing of the predetermined form in the

Pumping chamber 3 is constructed. As a result, a time delay between starting the dosing and output of working fluid is avoided or at least significantly reduced. FIG. 2 shows a second exemplary embodiment of a device according to the invention, with reference to which a second exemplary embodiment of the method according to the invention is described. The second embodiment of the device according to the invention and of the method according to the invention is fundamentally similar to the respective first exemplary embodiment. In the following, in order to avoid repetition, particular attention is paid to the differences: The device according to Figure 2 also has the above-described components metering pump 5, pressure control valve 1 1, pumping fluid reservoir 9, valves 13 and 14 and the compressed gas source 10 for providing a form Q on.

A pumping chamber 3 'of the device comprises an elastic bladder 23 formed by an elastic membrane. The elastic membrane is fixed on the inside to a wall of the pumping chamber 3 'fluid-tight and encloses an opening of the elastic bubble a pumping fluid opening 24 of the pumping chamber 3'. By means of the metering pump 5 is thus optionally pumping fluid via the pumping fluid port 24 into the elastic bladder 23 can be supplied or discharged from the elastic bladder.

The elastic bladder thus divides the pumping chamber 3 'into a pumping fluid area enclosed by the elastic bladder and a working fluid area outside the elastic bladder in the pumping chamber 3'.

In contrast to the device according to FIG. 1, the device according to FIG. 2 has a working fluid reservoir 16 which is designed to be pressure-stable and is fluid-conductively connected to the working fluid region of the pumping chamber 3 'via pressure-stable lines 18 and 18' via a shut-off valve 17. Furthermore, the pumping chamber 3 'on a vent valve 19, which is also fluidly connected to the working fluid region of the pumping chamber 3', wherein a vent line via the vent valve 19 opens into a collecting container 20.

For the first provision of working fluid in the working fluid area of the still empty pressure-stable and dimensionally stable pumping chamber 3 ', first the venting valve 19 is opened and pumping fluid is introduced into the elastic bladder 23 by means of the metering pump 5 so that the elastic bladder 23 expands and any gas present in the working fluid area of the pumping chamber 3 'is discharged via the vent line and the vent valve 19, then the vent valve 1 9 is closed and the shut-off valve 17 is opened so that when pumping fluid from the elastic bladder 23 by means of the metering pump 5, the elastic bladder 23 is reduced in volume and thus working fluid from the working fluid reservoir 16 flows into the working fluid region of the pumping chamber 3 '. In this case, by means of a compressed gas source 26 via a further shut-off valve 25 a constant pressure in the working fluid reservoir 16 and thus also in the region of the pumping chamber 3 'predetermined to prevent that during filling at the working fluid discharge port 22, a negative pressure. For complete venting of the pumping chamber 3 ', this process can be repeated.

After providing the working fluid in the pumping chamber 3 ', the shut-off valve 17 is closed. It is within the scope of the invention, when filling the working fluid region of the pumping chamber 3 'to close the working fluid discharge opening 22 of the pumping chamber 3' by means of a further valve. However, it is also possible to provide such a valve at the working fluid discharge opening 22 and instead to select the admission pressure by means of the compressed gas source 26 always during the filling process equal to the ambient pressure, so that at the working fluid discharge opening 22 neither an excess nor a negative pressure.

After filling the working fluid region of the pumping chamber 3 'with working fluid V, the valves 17 and 19 are closed and it is in a step B by means of the metering pump 5 as previously described in Figure 1 pumping fluid 6 from the pumping fluid reservoir 9 into the pumping chamber 3', that is in the elastic bladder 23 introduced. The elastic bladder 23 expands accordingly and displaces working fluid discharged from the working fluid opening 22.

Figure 3 shows a third embodiment of a device according to the invention, which is similar in basic construction to the first embodiment shown in FIG. With reference to the third embodiment of a device according to the invention, a third embodiment of a method according to the invention will be described, which thus also resembles the first embodiment of a method according to the invention in the basic sequence.

It is essential that the device according to FIG. 3 has a volumetric translation device 30. This comprises a first cylinder-piston unit 31 and a second cylinder-piston unit 32. A first volume 31 a of the first unit 31 is fluid-conducting with a pump fluid inlet Opening a pumping chamber connected. A first volume 32a of the second unit 32 is connected to a metering pump for conveying pumping fluid. Furthermore, a bypass line for bypassing the units 31 and 32 is provided between the metering pump and the pumping chamber, which bypass line has a shut-off valve 28. Between the shut-off valve 28 and metering pump, a branch is provided in the flow path, which leads via a further shut-off valve 29 to the first volume 32 a of the unit 32.

For filling the pumping fluid region of the pumping chamber and for removing pumping fluid from the pumping chamber, by closing the valve 29 and opening the valve 28 as described above, pumping fluid can be fed into the pumping chamber or removed from the pumping chamber by means of the metering pump.

During the metering operation, in the device according to FIG. 3, the valve 28 is closed and the valve 29 is opened. During the dosing process, pumping of pumping fluid by means of the dosing pump into the pumping chamber thus takes place only indirectly.

By means of the metering pump pumping fluid is conveyed via the open valve 29 into the first volume 32a of the unit 32. A piston of the unit 33 is mechanically connected to a piston of the unit 31. An expansion of the first volume 32a thus results due to the mechanically coupled piston displacement to a reduction of the first volume 31 a of the unit 31 and corresponding to the introduction of pumping fluid from the first volume 31 a in the pumping chamber.

Since the cross-sectional area of the piston of the unit 32 is twice as large as the cross-sectional area of the piston of the unit 31, this results in a volumetric ratio in the ratio 2: 1:

In order to promote a predetermined volume A from the first volume 31 a of the unit 31 in the pumping chamber, thus twice as large volume, that is 2a, pumped by pumping fluid by means of the metering pump into the first volume 32 a of the unit 32 must be promoted. As a result, the dosing accuracy is further increased because the absolute error of the dosing amount is smaller for larger volumes. FIG. 4 shows a fourth exemplary embodiment, which in principle is similar in construction to the second exemplary embodiments. Again, a volumetric translation unit 30 with a first unit 31 and a second unit 32 and a valve 28 and a bypass line and a valve 29 is additionally arranged. The operation follows analogously to the method described with reference to FIG. 2, the volumetric translation as described with respect to FIG. 3 being used to increase the dosing accuracy when the processing fluid is dispensed.

All embodiments have in common that due to the pressure-stable and dimensionally stable design of the pumping chamber (3, 3 ') and the connecting elements (8) to the metering pump (5) and due to the fact that pumping fluid (6, 6') and working fluid (3, 3 ') in the region between the metering pump (5) and the working fluid opening (4, 4') share the same volume, the volume flowing into the pumping chamber (3, 3 ') at all times at the working fluid openings (4, 4') outflowing volume corresponds.

Claims

claims

Method for dosing a working fluid (1, 1 '), comprising the following method steps:

A providing the working fluid (1,) within a pressure-stable and dimensionally stable pumping chamber (3, 3 ');

B supplying a predetermined volume of an incompressible pumping fluid (6, 6 ') by means of a metering pump (5) into the pumping chamber (3, 3'), wherein in the pumping chamber (3, 3 ') at an interface between pumping fluid (6, 6' ) and working fluid, which interface divides the pumping chamber (3, 3 ') into a pumping fluid region and a working fluid region,

I, an interfacial flexible membrane in the

Pumping chamber (3, 3 ') is arranged, or

II. The pumping fluid (6, 6 ') at the interface directly to the

Working fluid adjacent. and discharging the working fluid (1, 1 ') from at least one working fluid opening (4, 4') of the pumping chamber (3, 3 ") by passing the working fluid (1, 1 ') in the pumping chamber (3, 3') Feeding the pumping fluid (6, 6 ') is displaced.

Method according to claim 1,

characterized,

in a method step C after method step B, the pressure of the pumping chamber (3, 3 ') is adjusted to an ambient pressure by opening a relief valve (7, 19), which compensates pressure with an environment and the pumping fluid region and / or the working fluid region Pumping chamber (3, 3 ') is connected, preferably, that at least before step B, preferably before the process Steps A and B of the relief valve (7,19) is closed.

Method according to one of the preceding claims,

characterized,

in method step B, before the fluid is dispensed, the working fluid area is subjected to a pre-pressure which is in the range of 50% to 95%, preferably 85% to 95%, more preferably approximately 90% of the pressure necessary to dispense working fluid.

Method according to one of the preceding claims,

characterized,

in process step B, pumping fluid (6, 6 ') is supplied from a pumping fluid reservoir (9) on the suction side, which pumped fluid reservoir (9) is pressure-stable with respect to the ambient pressure and which pumping fluid reservoir (9) is pressurized by means of a compressed gas source (10 ) Gas under a constant pressure for maintaining a predetermined pressure in the pumping fluid reservoir (9) and thus for maintaining a predetermined admission pressure on the suction side (12) of the dosing pump (5) is supplied, in particular that the admission pressure at least 90% of the output of Working fluid necessary pressure is.

Method according to one of the preceding claims,

characterized,

that in process step A pumping fluid (6, 6 ') is removed from the pumping chamber (3, 3') by means of the metering pump (5) in order to generate a negative pressure in the pumping chamber (3, 3 ') and working fluid (1, 1' ) from a working fluid reservoir (16) into the pumping chamber (3, 3 ').

Method according to one of the preceding claims,

characterized,

the volume (ΔΥ) of the pumping chamber (3, 3 ') which is not occupied by the working fluid (1, 1') is filled with pumping fluid (6, 6 ') between process steps A and B, optionally in the pumping chamber (3, 3 ') existing gas via a vent valve (7, 1 9) from the pumping chamber (3, 3 ') is discharged.

7. The method according to any one of the preceding claims,

characterized,

the working fluid is a compressible fluid, in particular a compressible gas.

8. Device (A, A ') for dispensing a working fluid (1, 1'),

comprising a pressure-stable and dimensionally stable pumping chamber (3, 3 ') and a metering pump (5) for conveying an incompressible pumping fluid (6, 6'), wherein the metering pump (5) via a pressure-stable and dimensionally stable fluid line (8) with a pumping fluid opening (24) the pumping chamber (3, 3 ') is connected to supply and / or remove pumping fluid {6, 6') and

the pumping chamber (3, 3 ') has at least one working fluid opening (4, 4') in order to supply and / or remove a working fluid (1, 1 '),

and wherein the pumping chamber {3, 3 ') is designed such that in use an interface between pumping fluid (6, 6) and working fluid (1, 1') is formed in the pumping chamber (3, 3), which interface is the pumping chamber (3). 3, 3 ') into a pumping fluid region, into which the pumping fluid orifice (24) opens and divides a working fluid region, into which the working fluid orifice (4, 4') opens, wherein

I. an interfacial flexible membrane in the

Pumping chamber (3, 3 ') is arranged, or

II. The pumping fluid (6, 6 ¹ ) at the interface directly to the

Working fluid (1, 1 ') adjacent.

9. Device (A, A ') according to claim 8,

characterized,

in that the pumping chamber (3, 3 ') for receiving a working fluid (1, 1') containing cartridge (2) is formed with an at least partially flexible cartridge wall, which cartridge wall forms the flexible membrane according to Variant I.

1 0. Device (A, A ') according to claim 8,

characterized,

that according to variant I, the flexible membrane in the pumping chamber (3, 3 ') with one or more walls of the pumping chamber (3, 3') is arranged fluid-tightly connected.

1 1. Device (A, A ') according to one of claims 8 to 10,

characterized,

in that at least the flow path between the metering pump (5) and the pumping chamber (3, 3 ') is pressure-stable relative to the ambient pressure acting on the device (A, A'), preferably that the metering pump (5) is fluid-conductively connected to the pumping chamber (3) via pressure-stable lines , 3 ') is connected.

12. Device (A, A ') according to one of claims 8 to 1 1,

characterized,

the pumping chamber (3, 3) has a pressure relief valve and / or venting valve (7, 19) fluidly connected to the pumping fluid region.

13. Device (A, A ') according to one of claims 8 to 12,

characterized,

in that the metering pump (5) is fluid-conductively connected on the one hand to the pumping fluid opening (24) of the pumping chamber (3, 3 ') and on the other hand to a pumping fluid reservoir (9), preferably in that the pumping fluid reservoir (9) is pressure-stable closed or closable relative to the ambient pressure ,

14. Device (A, A ') according to claim 13,

characterized,

that between the pump fluid reservoir (9) and metering pump (5) a pressure regulating valve (1 1) is arranged.

15. Device (A, A ') according to one of claims 13 to 14,

characterized,

in that a compressed gas source (10) is in fluid conduction with the pump fluid reservoir (9) connected is.

16. Device (A, A ') according to one of claims 8 to 1 5,

characterized,

a working fluid reservoir (16) is provided, which is fluid-conductively connected to the working fluid region of the pumping chamber (3, 3 '), preferably that at least the flow path between working fluid reservoir (16) and pumping chamber (3, 3') is pressure-stable with respect to the device ( A, A '), in particular that the working fluid reservoir (16) is fluid-conductively connected to the pumping chamber (3, 3') by means of pressure-stable lines.

17. Device (A, A ') according to claim 16,

characterized,

the working fluid reservoir (16) is pressure-stable closed or closable relative to the ambient pressure.

18. Device (A, A ') according to one of claims 16 to 17,

characterized,

in that a compressed gas source (10) is connected in a fluid-conducting manner to the working fluid reservoir (16).

19. Use of a device according to one of claims 8 to 18

and / or a method according to one of claims 1 to 4 for producing a photovoltaic solar cell, in particular for applying a paste containing metal particles to a semi-conductor substrate for producing a contacting structure.