FLUID DEVICE

A fluid device has at least one valve unit and at least one recirculation unit, each having a fluid chamber, which channels are fluidically connected to one another via at least one connection channel. The at least one feed channel discharges into the fluid chamber of the valve unit and a discharge channel discharges into the fluid chamber of the recirculation unit. Each of the fluid chambers is delimited by an elastically deformable diaphragm, and the valve unit and the recirculation unit each contain an actuation unit through which the associated valve diaphragm or recirculation diaphragm can be adjusted within the meaning of a change in volume of the associated fluid chamber. A fluidic connection can be established between the feed channel and the connection channel by the valve diaphragm and that a continuous fluidic connection exists between the connection channel and the discharge channel via the fluid chamber.

This application claims priority to German Patent Application No. 102023119300.7 filed Jul. 21, 2023, which is incorporated by reference.

The invention relates to a fluid device with at least one valve unit and at least one recirculation unit, each having a fluid chamber designed to receive a fluid.

Such fluid devices, also called suck-back units, have already been known for a long time, for example from JP H03-12917. There, a fluid device is described which is used during the production of semiconductors, offering the possibility of sucking back a fluid located in a fluid channel in order to prevent undesired dripping at a discharge opening. The suck-back effect can be caused by a negative pressure which can be generated in a fluid chamber of the fluid device to which the fluid channel is connected. The fluid chamber is delimited by an elastically deformable diaphragm.

A fluid device is likewise known from DE 10 2020 209 594 B3, in which the diaphragm can be actuated by means of a piezo actuator.

SUMMARY OF THE INVENTION

The object of the invention is to produce a fluid device of the type named at the outset, which is designed to be simple and compact and can be operated reliably.

This object is achieved by a fluid device with the features of independent claim1. Developments of the invention are shown in the dependent claims.

The fluid device according to the invention possesses at least one valve unit and at least one recirculation unit, each having a fluid chamber designed to receive a fluid, which channels are fluidically connected to one another via at least one connection channel, wherein at least one feed channel discharges into the fluid chamber of the valve unit and a discharge channel discharges into the fluid chamber of the recirculation unit, and wherein each of the fluid chambers is delimited by an elastically deformable diaphragm, and wherein the valve unit and the recirculation unit each contain an actuation unit through which the associated valve diaphragm or recirculation diaphragm can be adjusted within the meaning of a change in volume of the associated fluid chamber, wherein a fluidic connection can be established between the feed channel and the connection channel by the valve diaphragm and that a continuous fluidic connection exists between the connection channel and the discharge channel via the fluid chamber of the recirculation unit.

Both the valve unit and the recirculation unit each have an elastically deformable diaphragm and an actuation unit for the diaphragm. The valve unit and the recirculation unit are thus components which are designed to be substantially identical in construction, which minimises production costs. The fluid device is suitable for carrying out media separation through the valve unit, whereby it can be used as a suck-back unit during metering or liquid handling in the semiconductor industry, or in the med lab field. For example, the fluid device is suitable to be used with microtiter plates in liquid handling.

In a development of the invention, valve diaphragm and recirculation diaphragm are arranged in diaphragm planes parallel to one another. Expediently, valve unit and recirculation unit are arranged behind one another in alignment direction, wherein the valve diaphragm and the recirculation diaphragm are then likewise arranged behind one another in alignment direction.

In particularly preferred manner, valve diaphragm and recirculation diaphragm are identical in design.

The material of the diaphragm expediently complies with the medium with which the diaphragm comes into contact. For example, thermoplastics such as polyaryletherketone (PEEK), polytetrafluoroethylene (PTFE), perfluoroalkoxy polymers (PFA) or rubbers, such as fluorine rubber (FKM), are suitable here.

In a development of the invention, the diaphragm centres of valve diaphragm and recirculation diaphragm lie on a common diaphragm axis.

In particularly preferred manner, the fluid device has a base plate, with a fitting surface on which the valve unit and the recirculation unit are arranged and attached by means of attachment means. However, in principle, the use of the fluid device without such a base plate would also be conceivable.

In particularly preferred manner, the diaphragm planes of the valve diaphragm and of the recirculation diaphragm are aligned perpendicular to the fitting surface. It is thus possible to arrange at least one valve unit and at least one recirculation unit one behind another in alignment direction on the fitting surface, wherein the diaphragm planes of each of the valve units or recirculation units can then likewise be aligned perpendicular to the fitting surface one behind another in alignment direction. This design is particularly space-saving.

In the development of the invention, the base plate has at least one supply opening for feeding the fluid and a discharge opening for discharging the fluid is provided, wherein a fluid channel system communicating with the channels in the valve unit and the recirculation unit extends between the supply opening and the discharge opening.

In a development of the invention, the discharge opening is designed at a discharge nozzle arranged at the base plate and belonging to the fluid device.

It is possible that a feed opening of the feed channel and a connection channel opening of the connection channel of the valve unit are arranged on the same side of the valve unit, preferably on a bottom side of the valve unit facing the fitting surfaces.

It is also possible that a connection channel opening of the connection channel and a discharge channel opening of the discharge channel of the recirculation unit are arranged on the same side on the recirculation unit, preferably on a bottom side of the valve unit facing the fitting surface.

In a development of the invention, the fluid chambers of the valve unit and of the recirculation unit have the same diameter. In particularly preferred manner, the actuation unit of the valve unit and the actuation unit of the recirculation unit are identical in design.

This leads to a reduction in production costs, as the components of the actuation unit can be produced independently of the type of unit in which they are later used.

In a development of the invention, the actuation unit has an actuation power unit and an actuation member connected to the diaphragm such that an actuation movement transferred by the actuation power unit to the actuation member prompts the actuation member to adopt different positions so that the associated diaphragm causes a volume change in the fluid chamber by elastic deformation.

In a development of the invention, the actuation member is designed as an in particular plate-shaped actuating lever, firmly clamped on one side via a lever bearing, is coupled to the associated diaphragm via a catch element and at its free lever end is coupled to the actuation power unit such that the actuation movement transferred by the actuation power unit prompts the actuating lever to pivot. The actuation unit is thus overall relatively simply and thus robustly constructed.

In particularly preferred manner the actuation power unit is designed as an electric actuation power unit, in particular as an actuation power unit in the form of a step motor or DC motor.

In particularly preferred manner, a longitudinal axis of the actuation unit is designed parallel to the fitting surface. In use condition, the actuation unit is thus designed transverse, whereby the overall height of the fluid device can remain relatively low.

In a development of the invention, the actuation power unit has an output shaft driven rotationally about an axis of rotation, which shaft is coupled to an eccentric element arranged eccentric to the axis of rotation, which element is coupled to the actuating lever, in particular the free lever end thereof.

In a development of the invention, a reset element for resetting the actuation member and the linked diaphragm is associated with the actuation member within the meaning of reducing the volume of the associated fluid chamber.

In particularly preferred manner, the reset element is designed as a spring, in particular a leaf spring. Expediently, the leaf spring is supported at both ends at a cover.

In a development of the invention, the fluid chamber of the valve has a hump-shaped channel which forms the valve seat which can be sealed by the associated diaphragm.

In a development of the invention, a stroke sensor is provided for determining the stroke of the actuation lever.

In particularly preferred manner, the free lever end of the actuation lever is associated with the stroke sensor, and the lever end measures the stroke of the lever end of the actuation lever.

It is possible to regulate the stroke path of the actuation lever via the stroke sensor within the meaning of regulating to the sensor signal, wherein specific voltage signals are associated with specific opening positions. If the predetermined sensor signal or voltage signal is not achieved, this indicates that the desired opening position has not been reached. It can then be readjusted until the desired opening position has been reached.

In a development of the invention, the fluid device has a housing which carries all assemblies.

It is possible that the fluid chambers of the valve unit and of the recirculation unit are designed in a fluid body which can be integrated simply into the housing, with the result that, for example in simple manner, a recirculation unit can be formed by exchanging the fluid body from a valve unit.

DETAILED DESCRIPTION OF THE INVENTION

FIGS.1to12show a preferred embodiment example of the fluid device11according to the invention. The fluid device11is used hereinafter by way of example as a metering device for liquid media. As shown by way of example inFIG.1, the fluid device can be used with microtiter plates12in the med lab field for liquid handling. This application is purely by way of example.

In the shown application, a microtiter plate12is thus provided which is shown by way of example in the form of a 96-well microtiter plate which thus has 96 cavities. The fluid device11has the task in selected of the cavities13to dispense a specific quantity of liquids. Self-evidently, it is also possible to use quite different sizes of microtiter plates12.

In any case, the task of the fluid device11is to dose a specific quantity of a liquid into the respective cavity13. As these are mostly relatively small quantities, in particular in the microlitre range, there is the need for the quantity to be dosed precisely. An undesired dripping at the discharge opening22of the fluid device11is absolutely to be avoided.

For this purpose, the fluid device11has at least one valve unit14and at least one recirculation unit15. As described in even more detail hereinafter, the valve unit14ensures that a fluid transit, in particular in the region of a valve seat, can alternately be opened or closed, wherein when the fluid passage is open, the fluid to be dosed, thus in the exemplary case the liquid, can arrive at the discharge opening22and there be dispensed into the associated cavity13. Upon actuation, the associated recirculation unit15produces a suck-back effect by means of negative pressure, whereby a fluid still located in the fluid channel is recirculated in order to prevent the previously described negative effect of the undesired dripping.

In the shown exemplary case the fluid device11consists of a single valve unit14and a single recirculation unit15which are arranged one behind another along an alignment direction16(FIG.2). It is self-evidently possible to use several valve units and several recirculation units, wherein in this case one of the recirculation units is then also associated with a respective valve unit.

In the shown exemplary case, the fluid device11possesses, in addition to the valve unit14and the recirculation unit15, a base plate17which has on the top side a fitting surface18and on the bottom side a discharge interface19.

As shown in particular inFIGS.1and2, the valve unit14and the recirculation unit15are attached to the fitting surface18of the base plate17by means of attachment means20. In the shown exemplary case, a screw connection is chosen here between the valve unit14or the recirculation unit15respectively and the base plate17, while it is self-evidently also possible to use other types of attachment means, for example a click, snap or clip connection which can be actuated without using any tools.

As shown in particular inFIG.2, the base plate17possesses at least one supply opening (not shown) for feeding the medium or fluid in the exemplary case of the liquid. As shown inFIG.2, a feed line99is arranged at the supply opening which is designed by way of example as a feed tube. The feed tube can for example be coupled with a tube connector to the supply opening.

It is possible that the alignment direction16runs not as shown by way of example inFIG.2substantially parallel to the feed line99but perpendicular thereto, for example in the event that a minimum grid dimension is required parallel to the feed line99.

The base plate17also possesses an outlet opening (not shown) for fluid on the bottom side discharge interface19. A fluid channel system (not shown) communicating with the channels in the valve unit14and the recirculation unit15extends between the supply opening and the outlet opening.

As also shown inFIG.2, a discharge nozzle21is arranged at the outlet opening on the underside discharge interface19of the base plate17, which nozzle is fluidically connected to the outlet opening. A fluid channel (not shown) which ends at a discharge opening22arranged at the free end of the discharge nozzle21extends through the discharge nozzle21.

As in particular the synopsis ofFIGS.4,5,6and10shows, the valve unit14and the recirculation unit15each possess a fluid chamber23,24.

As shown in particular inFIGS.3,4and5, each of the fluid chambers23,24is designed in a fluid body25,26, while each of which in turn is a component of a valve unit housing27or recirculation unit housing28.

An essential aspect of the invention is that each of the fluid chambers23,24is delimited by an elastically deformable diaphragm29,30. In the case of the valve unit14, a valve diaphragm29thus delimits the fluid chamber23of the valve unit14and in the case of the recirculation unit15, a recirculation diaphragm30delimits the fluid chamber24of the recirculation unit15.

A further important aspect of the invention is that the valve unit14on the one hand and recirculation unit15on the other hand are identical in design, with the exception of the design of the fluid chambers24,25.

The structure of the valve unit14described below accordingly also applies to the recirculation unit15, with the exception of the structure of the fluid chamber23,24.

The valve unit14accordingly possesses the already mentioned valve unit housing27. The valve unit housing27is designed to be cuboidal in the exemplary case. It possesses a front side31and a rear side32opposite the front side31. Furthermore, the valve unit housing possesses a top side33and a bottom side34oriented opposite thereto, which bottom side abuts against the fitting surface18of the base plate17in the mounted use condition. Finally, the valve unit housing27possesses two end sides35,36arranged opposite one another.

To attach the valve unit housing27to the fitting surface18, an attachment flange37can for example be provided pointing outwards from the end side35, wherein on the opposite end side35a further attachment flange38is provided, which, however, is developed on the front side31not as a projection but as a notch developed on the front edge of the valve unit housing27.

As shown in particular inFIG.3, each of the attachment flanges37,38have through bores (not shown) which are penetrated by attachment screws39, which in turn are screwed to the base plate17in associated screw holes. In this way, the valve unit14is attached to the fitting surface18of the base plate17.

An important aspect is that the already mentioned fluid body25is attached as a separate component likewise at the valve unit housing27.

As already mentioned, the fluid chamber24of the valve unit14is designed in the fluid body25of the valve unit14.

As in particular the synopsis ofFIGS.3,6and7shows, the fluid body25of the valve unit14is designed to be like an ‘L’ and possesses a base section40and an edge section41projecting at right angles from the base section. The edge section41forms a part of the bottom side34of the valve unit14. This edge section41is flanked in wedge-like manner by both attachment flanges37,38arranged to the left and right thereof.

The fluid chamber23designed in the fluid body25of the valve unit14possesses a substantially circular cross-section, interrupted by a strut-like hump42projecting radially inwards, in which hump a feed channel43runs. The feed channel43extends from a feed opening44designed on the strut-like edge section41into the centre of the fluid chamber23, wherein a base channel section45of the feed channel43is aligned substantially perpendicular to the fitting surface18. A seat channel section46, designed in the embodiment example to be relatively short, is attached substantially at right angles to the base channel section45, which seat channel section leads into the fluid chamber23via a valve seat opening47. As shown in particular inFIG.6, the valve seat opening47is located at a valve seat48designed in particular to be cone-shaped, which valve seat is part of the hump42projecting inwards.

As also shown inFIGS.6and8, the valve diaphragm29is associated with the valve seat48, which diaphragm can open or close the valve seat opening47alternately in a manner explained in even more detail below. When the valve seat opening47is open, fluid can flow into the fluid chamber23of the valve unit14via the feed channel43. When the valve seat opening47is closed, the feed of fluid into the fluid chamber23is blocked, on the other hand.

Fluid is fed via the already mentioned feed line20which is connected to the base plate17. Fluid then arrives at the feed opening44of the valve unit via the channel system in the base plate17.

As shown in particular inFIG.7, a further channel, specifically a connection channel50, discharges into the valve chamber23of the valve unit14. Unlike the previously described feed channel43, this connection channel50does not, however, discharge into the fluid chamber23via a central hump42, but at the circumferential surface51of the fluid chamber23. The connection channel50extends proceeding from a connection channel opening52designed at the edge section41of the fluid body25in direction of the fluid chamber23and there discharges into the fluid chamber23via a discharge opening53.

Self-evidently it is possible to swap feed channel43and connection channel50, i.e. the fluid is fed via the connection channel50which would then become the feed channel.

As also shown inFIG.7, both of the previously described channels, thus the feed channel43and the connection channel50, lead to the wedge-like edge section41, i.e. the channels lead to the bottom side34of the valve unit14. As previously described, the valve unit14is mounted such that the bottom side34of the valve unit14and thus the wedge-shaped edge section41is in contact with the fitting surface of the base plate17. Openings (not shown) are designed on the fitting surface of the base plate17, communicating with the feed channel43and the connection channel50, in particular with the feed opening44and the connection channel opening42. At the interface between valve unit14and base plate17there is the need for a seal, which is formed for example by the sealing ring54shown by way of example inFIG.7.

As shown in particular inFIG.3, the fluid body25of the valve unit14is a component separate from the valve unit housing27and is therefore attached to the valve unit housing27via suitable attachment means55. For example a screw connection between the fluid body25and the valve unit housing27is suitable for this.

It is for example possible to design several attachment holes56at the base section40of the fluid body, for example four at the figure penetrated by the associated attachment screws57, which in turn are screwed into associated screw holes (not shown) on the valve unit housing27.

Overall, the fluid body25is a component in which the fluid chamber23is designed at the same time during production. The material of the fluid body is directed according to the type of fluid or medium used which is to be metered via the fluid device11. Expediently, the fluid body is a plastic component, wherein, if used in laboratories, for example polyetheretherketone (PEEK) is used as fluid body material, whereas, with semiconductor applications, the fluid body is more likely to be made of polytetrafluoroethylene or perfluoroalkoxy polymers (PFA).

As mentioned above, and shown by way of example inFIGS.6and8, the fluid chamber23of the valve unit14is delimited by a valve diaphragm29.

As shown in particular inFIG.6and also inFIG.8, the valve diaphragm29is inserted in the valve unit housing27in which an annular diaphragm edge section58designed in the manner of a bulb is inserted into an annular groove59, provided for this purpose and designed on the valve unit housing. The valve diaphragm29is then tensioned by attaching the fluid body25, while the diaphragm edge section58is thus tensioned between the fluid body25and the valve unit housing.

As also shown inFIG.6, the valve diaphragm29possesses a diaphragm centre60which is associated with the valve seat58and can close or open a valve seat opening47in a manner described in even more detail below. On the rear of the diaphragm centre60, thus facing away from the fluid chamber24, is an attachment interface61via which the valve diaphragm29is coupled to an associated actuation unit62. The actuation unit62serves to actuate the valve diaphragm29whereby, in addition to opening and closing the valve opening40, there is also a change in volume of the associated fluid chamber23.

The actuation unit62has an actuation power unit63and an actuation member64connected to the valve diaphragm29such that an actuation movement transferred by the actuation power unit62to the actuation member64prompts the actuation member64to adopt different positions so that the associated valve diaphragm causes a volume change in the fluid chamber23by elastic deformation.

As in particular the synopsis ofFIGS.4,5and6shows, in the shown exemplary case the actuation power unit63is an electric actuation power unit in the form of a step motor or DC motor. The actuation power unit63possesses a power unit housing65in which the components of the electric actuation power unit, not shown here in more detail, are accommodated. As shown inFIG.4, the power unit housing65is attached to one of the end sides35of the valve unit housing27. The actuation power unit63also has an output shaft67driven rotationally about an axis of rotation66, which shaft is coupled eccentrically to an eccentric element68arranged at the axis of rotation66.

As shown in particular inFIG.5, the eccentric element68is designed as an eccentric pin arranged on the front side of the output shaft67.

As also shown inFIG.6, the output shaft67is mounted rotatable in the valve power unit housing via a rolling bearing69, wherein the rolling bearing69is arranged, in particular pressed in, between a cover70, described in even more detail below, and a bearing party of the valve unit housing67. A further rolling bearing71is arranged at the eccentric element68, which bearing has a clearly smaller diameter than the previously described drive shaft rolling bearing69. This eccentric rolling bearing71is connected to the actuation member64. As shown in particular inFIG.5, the output shaft67projects out of the power unit housing65, wherein a bearing element72is arranged between the power unit housing and the drive shaft rolling bearings69, via which output shaft the actuation power unit is mounted on the previously described end side35of the valve unit housing27such that the end side has a slit73opening towards the upper side of the valve unit housing67, with the result that the housing region is divided into two clamping fingers in the region of the end side35, each of which fingers has a bent recess (not shown) and thus receive the bearing element72associated with the output shaft between them. The clamping fingers can move towards one another by means of a clamping screw74introduced from the front or rear side of the valve unit27into a clamping boring designed in one of the clamping fingers and screwed to the other clamping finger, whereby there is a clamping on the bearing element72, leaving the actuation power unit thus secured to the valve unit housing27.

As already mentioned above, the actuation unit62possesses an actuation member64which is designed in the exemplary case as an actuating lever. The actuating lever is designed to be plate-shaped and possesses a relatively long extended lever base section75, wherein an actuation surface77is designed in the region of the free lever end76directed to the fluid chamber, which surface is in contact with the eccentric rolling bearing71.

As shown in particular inFIG.4, the free lever end76, which simultaneously also forms the closure of the lever base section75, can be designed with a lever axle79aligned transverse to the longitudinal axis78of the actuation lever, at the bottom side of which lever axle is designed the actuation surface77.

The actuating lever is also clamped fast at its other lever end80opposite the free lever end76via a lever bearing81. For this, the actuating lever is kinked at the other lever end80and engages in a parabolic recess at the valve unit housing27where it is then firmly clamped.

An important aspect is that the actuation member64, thus in the exemplary case the actuating lever, is coupled to the valve diaphragm39. For this, the actuating lever possesses a coupling interface82in the region of its lever base section, which interface has a continuous hole83designed in the lever base section75. The continuous hole83is penetrated by a coupling pin84, which in turn is designed like a hammerhead at the bottom, and is thus part of the attachment interface61between the coupling pin84and the valve diaphragm29.

As shown for example inFIG.6, the valve diaphragm29possesses a pin85(FIGS.8and12) projecting upwards at its diaphragm centre60, which pin has a centric recess in which, depending on the type of groove and spring, the hammerhead section of the coupling pin64is arranged.

The result of this is that an actuation movement exerted on the valve diaphragm29, acting on the actuating lever and as a consequence of the actuation power unit62, is transferred to the valve diaphragm29.

As shown in particular inFIG.4, a reset element86for resetting the actuation member64and the linked diaphragm membrane29is associated with the actuation member64within the meaning of reducing the volume of the associated fluid chamber23.

In the exemplary case, the reset element is designed as a leaf spring. As also shown inFIG.6, the leaf spring is connected to the coupling pin84such that the leaf spring has a continuous hole87at the centre, and is placed with this continuous hole87on a bearing pin projecting upwards on the top side of the coupling pin84. The leaf spring possesses a curve, wherein the region of the leaf springs is arranged with the continuous hole87closer to the fluid chamber than the two opposite spring ends, each of which is supported at the inside of the already mentioned cover70. The diaphragm is pressed into a normally closed position by this arrangement, in which position the valve seat opening87is closed by the diaphragm. To open the valve seat opening47pressure must be applied against the spring force of the leaf spring.

The already mentioned cover70has several tasks. For one, it supports the leaf spring at the bottom, and for another it closes the fluid body25at the end. It also offers a screw connection as a means of attachment for the cover.

As also shown inFIG.4, an electronics element89is located on the end side35on which the actuation power unit63is also designed.

An important aspect is that a stroke sensor90for determining the stroke of the actuation lever is associated with the actuating lever. The free lever end76of the actuation lever is associated with the stroke sensor90, and the lever end measures the stroke of the lever end of the actuation lever.

The previously described lever axle79also serves further to provide a relatively large measuring surface to the stroke sensor90. The stroke sensor90is set up for contactless measurement of the stroke of the actuation lever, for example an inductive stroke sensor can be used.

As shown in particular inFIG.4, a covering hood91is provided for covering the actuation power unit63arranged at the end side35and the electronics component or the electronics element89. An electric voltage supply of the actuation power unit63can be set up via the covering hood91, for example via a through opening arranged on the end side of the cover hood.

As already mentioned, the recirculation unit15is identical in design to the valve unit14, with the exception of the different design of the fluid body26and the fluid chamber24. In so doing, all components of the valve unit14are also used in the recirculation unit15, with the result that they need not be described again here.

As can be seen in particular inFIG.10, the fluid chamber24of the recirculation unit is not penetrated with a strut-shaped hump. The cross-section of the fluid chamber24of the recirculation unit15is circular. A discharge channel93discharges into the fluid chamber25of the recirculation unit15. The discharge channel93extends between a discharge channel opening94at the edge section41of the fluid body26as far as a first discharge opening95in the region of the peripheral wall92of the fluid chamber24. As already mentioned, valve unit14and recirculation unit15are connected to one another via a connection channel50. The connection channel in the recirculation unit15extends from a connection channel opening96at the edge section41of the fluid body26as far as a second discharge opening97. It is possible that, as shown inFIG.10, the channel aligned centrally in the direction of the centre of the fluid chamber24functions as a discharge channel93and the other channel, arranged eccentric thereto, as a connection channel, but it would also be conceivable to provide the centric channel as a connection channel and the channel arranged eccentric hereto as a discharge channel.

An important aspect is that there is a continuous fluidic connection between the connection channel50and the discharge channel93here in the recirculation unit15. The recirculation diaphragm30associated here with the fluid chamber24thus serves merely to establish a volume enlargement or volume reduction. With a volume enlargement, a negative pressure is generated in the fluid chamber24, which negative pressure sucks the medium back via the discharge channel into the fluid chamber24, whereby undesired dripping in the region of the discharge opening22of the discharge nozzle21is prevented.

The function of the fluid device as a metering device in connection with a microtiter plate12can be described as follows:

Firstly, the fluid device is arranged with its discharge nozzle21over the cavity13to be filled. In this position, the valve diaphragm abuts against the valve seat28, meaning the valve seat opening47is thus closed. For metering, the actuation power unit is then set in motion, whereby the eccentric element68moves clockwise via the rotational movement of the output shaft. This movement of the eccentric element68acts on the free lever end76of the actuation lever which for its part is pivoted into the position shown inFIG.8. In so doing, the coupled-in valve diaphragm29is lifted from the valve seat48and fluid or medium to be dispensed or metered arrives in the fluid chamber23of the valve unit14via the feed channel. From there, fluid to be metered arrives back in the base plate17via the connection channel50, and from there in the base plate17via the connection channel50in the recirculation unit15in the fluid chamber24of the recirculation unit15via the channel system. From there, the fluid to be metered arrives back in the base plate17via the discharge channel83of the recirculation unit15and from there arrives at the discharge opening22via the channel arranged in the discharge nozzle and is dispensed from there into the associated cavity13.

It is possible to control or regulate the quantity to be metered via the degree of opening of the valve seat opening47. The stroke sensor90which measures on the free lever end can carry out the regulation. Different degrees of opening are associated with different voltage values of the stroke sensor in a previously carried out calibration run. Thus a voltage value of 5 volts can for example be associated with a 100% degree of opening.

With the metering process, the distance between the stroke sensor90and the free lever end is changed by actuating the actuation power unit63, and a voltage value is generated. As long as the voltage value remains for example not yet at the predetermined 5-volt limit, the degree of opening of 100% has not yet been reached. This means that the actuation power unit remains in operation until the aforementioned voltage value is achieved. The actuation power unit63is then switched off.

Once the quantity to be metered has been dispensed, the recirculation unit15is activated. For this, the actuation power unit of the recirculation unit15is activated, whereby the output shaft is placed into a rotational movement, entraining the eccentric element68. As a result, the coupled-in actuating lever is moved from the position shown inFIG.9into a position shown inFIG.12via the position shown inFIG.10, wherein the position of the actuation lever shown inFIG.12permits the recirculation diaphragm30to ensure the maximum volume enlargement of the fluid chamber, whereby a negative pressure is produced, with the result that fluid present in the discharge nozzle in the channel is recirculated into the fluid chamber24of the recirculation unit15via the discharge channel93, whereby subsequent dripping in the region of the discharge opening22of the discharge nozzle21is prevented. It is thus ensured that the predetermined intended fill level can also be maintained with precision.