Dosing device for dosing liquid

Abstract

The invention relates to a metering device (1) for metering a liquid, comprising a channel plate (2), in which a fluid channel (11) is formed, which extends between a supply connection (6) and an outlet connection (7); a supply valve (80) associated with the supply connection (7); and an outlet valve (82) associated with the outlet connection (7); and a control device (42) which is electrically connected to the supply valve (80) and the outlet valve (82), the outlet connection (6) being assigned a coupling (9) for coupling the pipetting tip (10), and the supply valve (80) and / or the outlet valve (82) being designed as a proportional valve.

Description

Technical Field

[0001] The invention relates to a metering device for metering a liquid. Background Art

[0002] DE 10 2020 205 073 A1 discloses a metering device for metering a liquid, the metering device comprising: a fluid unit for selectively providing overpressure and negative pressure acting on a working gas received in a fluid channel, the fluid channel being connected to the fluid unit at a first end region, and the fluid channel comprising a second end region configured to receive and output a predefined amount of fluid; a first valve device and a second valve device, which are arranged spaced apart from each other along the fluid channel and are respectively configured to selectively block or release the fluid channel so as to construct a fluid reservoir defined by the two valve devices and provided for storing the working gas in the fluid channel; a control device for actuating the valve device, wherein a pressure sensor is assigned to the fluid reservoir, the pressure sensor being configured to provide a pressure signal according to the working gas pressure and being electrically connected to the control device. Summary of the invention

[0003] The object of the present invention is to provide a metering device with which a higher metering accuracy can be achieved.

[0004] This object is achieved for a metering device of the type mentioned at the outset according to the following features: a metering device for metering a liquid, the metering device comprising: a channel plate, in which a fluid channel is constructed, which fluid channel extends between a supply connector and an outlet connector; a supply valve assigned to the supply connector; and an outlet valve assigned to the outlet connector; and a control device, which is electrically connected to the supply valve and the outlet valve, wherein the outlet connector is assigned a connector for coupling a pipette tip, and wherein the supply valve and / or the outlet valve are constructed as proportional valves.

[0005] The channel plate, which can also be referred to as a base body, is penetrated by a fluid channel, which is designed for a fluid-communicating connection between a supply connection and an outlet connection. For example, a fluid module, which is designed in particular as a combination of a fluid source and a fluid sink, can be connected to the supply connection, by means of which a pressurized fluid and a negative pressure can be provided to the fluid channel, depending on the selection. For example, the channel plate is designed in one piece or in multiple parts, in particular as an injection molded part.

[0006] The outlet connector is provided with a coupling, which is configured to couple a pipette tip. A pipette tip is a tube section preferably made of plastic material, which is configured to taper in a conical manner and is configured to temporarily receive a liquid. Such a pipette tip is particularly used to dose liquids in the field of laboratory technology. The coupling structure assigned to the outlet connector for coupling a pipette tip is configured to receive the pipette tip in a fluid-tight manner, so that not only the fluid loaded with pressure but also the liquid received in the pipette tip cannot flow out between the coupling and the pipette tip.

[0007] The purpose of the supply valve assigned to the supply connection is to selectively open or close the fluid connection between the fluid module that can be connected to the supply connection and the section of the fluid channel that extends between the supply valve and the outlet valve. The purpose of the supply valve is thus to release or prevent the corresponding overpressure or negative pressure of the fluid channel, depending on the overpressure or negative pressure provided by the fluid module at the supply connection.

[0008] The purpose of the outlet valve assigned to the outlet connector is to selectively open or close the fluidic connection between the section of the fluid channel extending between the supply connector and the outlet valve and the outlet connector with the associated coupling. The purpose of the outlet valve is thus to selectively release or prevent pressure equalization between the environment of the metering device and the fluid channel, wherein during this pressure equalization, liquid can also be sucked into a pipette tip that can be placed on the coupling or discharged from the pipette tip.

[0009] Here, at least one valve from the group of supply valves, outlet valves, etc. is designed as a proportional valve, wherein, depending on the electrical control signal provided by the control device, a predeterminable valve opening can be provided by the proportional valve. Here, the proportional valve can be adjusted continuously between a completely closed functional state and a completely open functional state. Preferably, it is provided that there is a proportional relationship between the control signal and the functional state of the proportional valve, the control signal being in particular a control voltage that can be predetermined by the control device or a control current that can be predetermined by the control device. However, depending on the structural design of the proportional valve and an actuator belonging to the proportional valve (the actuator is responsible for converting the electrical energy provided by the control device into a mechanical movement), a non-proportional relationship between the control signal and the functional state of the proportional valve can exist instead of a proportional relationship.

[0010] The control device is, for example, configured as a microprocessor or microcontroller and is configured to implement a stored computer program. Preferably, the control device is connected to a superior control device, which is configured to provide control instructions to the control device to cause appropriate changes in the functional states of the supply valve and the outlet valve. Such a superior control device can be, for example, a machine control device of a laboratory automation device, which, for example, has a receiving surface for a large number of sample containers and a manipulator for the one-dimensional, two-dimensional or three-dimensional relative movement of the dosing device relative to the sample container. As an alternative, the control device can be connected to a switching device, especially fixed at the channel plate, which can be operated by an operator to provide the switch instructions for the supply valve and the outlet valve directly to the control device.

[0011] Advantageous developments of the invention are the subject matter of the dependent claims.

[0012] It is suitable that the fluid channel is connected to the negative pressure connector constructed at the channel plate, and the negative pressure connector is allocated with a negative pressure valve, which is particularly constructed as a proportional valve, and the negative pressure valve is electrically connected to the control device. Instead of a fluid module that is selectively constructed to provide an overpressure or negative pressure at the supply connector, an additional negative pressure connector can be used to connect a fluid source that is only provided for providing an overpressure to the supply connector, while a fluid sink that is only provided for providing a negative pressure is connected to the negative pressure connector. Thus, due to a shorter fluid stroke, it is possible to provide an overpressure or negative pressure to the fluid channel of the channel plate more quickly. As a result, for example, the metering device can be switched more quickly between the suction process for liquid into the pipette tip and the output process of liquid from the pipette tip. It is preferably provided that the negative pressure valve is constructed as a proportional valve so that it can be continuously adjusted by the control device between a fully closed state and a fully open state in a manner similar to the supply valve and / or outlet valve.

[0013] Preferably, it is provided that at least one valve from the group of supply valves, outlet valves, vacuum valves is constructed as a piezoelectric valve, preferably as a piezoelectric bending valve, in particular as a three-position three-way piezoelectric bending valve. By using a piezoelectric valve with at least one actuator made of piezoelectric material, a compact design can be achieved for the corresponding valve. In addition, compared with magnetic valves, piezoelectric valves have significantly less self-heating, because piezoelectric valves are operated with high voltages (in particular greater than 300 V) but with low currents. As a result, the heating of the metering device, the pipette tip connected thereto, and the liquid received in the pipette tip can be kept at a low level.

[0014] In an advantageous embodiment of the piezoelectric valve, the piezoelectric actuator is constructed in a strip shape and applied to a carrier material, especially spring steel, which is also constructed in a strip shape. By applying a suitable control voltage to the piezoelectric actuator, the curvature of the composite structure composed of the piezoelectric actuator and the carrier material, which is also called a piezoelectric bender, can be influenced. Thus, for example, a sealing element arranged at the piezoelectric bender can be optionally placed in a sealed manner on a valve seat constructed in a fluid channel, or the sealing element can be lifted from the valve seat. It is particularly advantageous that such a piezoelectric bender can be bent in opposite directions to each other by a suitable arrangement of multiple piezoelectric layers on the carrier material and has multiple sealing elements, thereby realizing a three-way three-way valve function. Such a proportional valve, for example, has a first inlet connection, a second inlet connection and a working connection, wherein, depending on the electrical control of the piezoelectric bender, the fluid-connected connection between the first inlet connection and the working connection or between the second inlet connection and the working connection can be optionally closed or released.

[0015] For a metering device, such a 3 / 3-way piezo valve can be used in such a way that the supply valve and the vacuum valve are accommodated together in a first valve housing, which has a first inlet connection connected to the supply connection, and a second inlet connection connected to the vacuum connection, and a first working connection is formed on the first valve housing, which is connected to the outlet valve. With such a 3 / 3-way piezo valve, a freely selectable and rapidly switchable pressure or vacuum application can be provided at the working connections, provided that a fluid source is connected to the supply connection and a fluid sink is connected to the vacuum connection.

[0016] In a further development of the invention, it is provided that the outlet valve is accommodated in a second valve housing, which has a second inlet connection connected to the first working connection of the first valve housing, and which has a second working connection connected to the outlet connection. It is preferably provided that the outlet valve is also designed as a 3 / 3-way piezo valve, so that the valve of the metering device is realized as a universal part. However, for the outlet valve, only the second inlet connection and the working connection are used, while the first inlet connection remains unused. Correspondingly, the outlet valve is operated only as a 2 / 2-way piezo valve.

[0017] In another design of the present invention, it is provided that the fluid channel has a first valve groove configured to receive the first valve housing and a second valve groove configured to receive the second valve housing. The first valve groove and the second valve groove are introduced into the channel plate as recesses. It is preferably provided that the section of the fluid channel starting from the supply connector and the section of the fluid channel starting from the negative pressure connector are passed into the first valve groove. In addition, it is provided that another section of the fluid channel extends between the first valve groove and the second valve groove, and the other section passes through the two valve grooves. In addition, it is provided that a section of the fluid channel connected to the outlet connector extends from the second valve groove. The first valve groove and the second valve groove are constructed so that the first valve housing and the second valve housing are connected to the corresponding sections of the fluid channel with their corresponding inlet connectors and working connectors. It is preferred that the first valve groove and the second valve groove are constructed so that with the first valve housing or the second valve housing being installed, a fluid-tight connection is achieved between the inlet connector and the assigned section of the fluid channel and between the working connector and the assigned section of the fluid channel relative to the environment.

[0018] Preferably, it is provided that the maximum metering volume is determined by the first valve housing, the second valve housing and the fluid channel section extending between the first valve housing and the second valve housing, and that the volume share of the fluid channel section in the maximum metering volume is less than 20 percent, preferably less than 10 percent. In particular, it is provided that the maximum metering volume is determined by the first valve housing, the fluid channel section extending between the first valve housing and the second valve housing, the second valve housing and, if necessary, by the section of the fluid channel extending between the second valve housing and the outlet connection. In this case, the volume share of the fluid channel section in the maximum metering volume is less than 20 percent, in particular less than 10 percent. Since the valve housing must be manufactured with high precision for the prescribed function of the corresponding valve, it is advantageous for the definition of the maximum metering volume that the maximum metering volume is mainly determined by the valve housing, so that slightly lower requirements can be placed on the precision of the fluid channel section.

[0019] It is expedient that a first pressure sensor arrangement electrically connected to the control device is arranged between the first valve spool and the second valve spool, and a second pressure sensor arrangement electrically connected to the control device is assigned to the outlet connection. The first pressure sensor arrangement serves to detect the pressure in the metering volume determined by the first valve housing, the second valve housing and the fluid channel section located therebetween, wherein the suction process for liquid into the pipette tip or the discharge process from the pipette tip is decisively determined by the pressure present in the metering volume. The second pressure sensor arrangement serves to detect the pressure actually present at the pipette tip, so that a particularly advantageous regulation can be made for the metering process.

[0020] In another embodiment of the present invention, it is provided that the first pressure sensor arrangement comprises a first pressure sensor with a first measuring range and a second pressure sensor with a second measuring range, wherein the first measuring range and the second measuring range have an intersection. By using pressure sensors with different measuring ranges for the two first pressure sensor arrangements, an advantageous improvement in the measuring accuracy is achieved compared to a pressure sensor arrangement with only a single pressure sensor, since, for example, the first pressure sensor can have a high accuracy in the negative pressure range and the second pressure sensor can have a high accuracy in the overpressure range. In this case, the measuring ranges of the two pressure sensors are selected so that they overlap. As a result, the function of the two pressure sensors can be controlled by a control device electrically connected to the two pressure sensors by comparing the sensor signals in the pressure range in which the two measuring ranges overlap.

[0021] In an advantageous development of the invention, it is provided that a delivery pump, in particular designed as a diaphragm pump, is assigned to the supply connection and / or a vacuum pump, in particular designed as a diaphragm pump, is assigned to the vacuum connection. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] An advantageous embodiment of the present invention is shown in the accompanying drawings. Here, it is shown:

[0023] Figure 1 shows a strictly schematic overview of a metering device having a channel plate, a valve arrangement received in the channel plate, and a control device; and

[0024] Figure 2 A strictly schematic sectional view of a valve arrangement is shown, which has a piezoelectric bender accommodated therein. DETAILED DESCRIPTION

[0025] Figure 1 The dosing device 1 schematically shown in the figure is designed for use in laboratory automation and for dosing liquid samples and reagents. By way of example, it can be provided that the dosing device 1 is mounted on a manipulator (not shown) of the laboratory automation device so that, for example, the dosing device 1 can be moved on a surface on which a sample container (not shown) is arranged in order to receive a liquid from a sample container or to dispense a liquid into a sample container.

[0026] The metering device 1 has a channel plate 2, which can also be regarded as the base body of the metering device 1 and which can be accommodated in a housing (not shown) if necessary. The channel plate 2 is assigned a first valve arrangement 3, a second valve arrangement 4 and a control device 5. In addition, the channel plate 2 has a supply connection 6, an outlet connection 7 and a negative pressure connection 8. A coupling 9, which is only schematically shown, is arranged at the outlet connection 7, to which a pipette tip 10 is coupled.

[0027] The channel plate 2 is penetrated by a fluid channel 11, which is determined by a first fluid channel section 21, a second fluid channel section 22, a third fluid channel section 23 and a fourth fluid channel section 24. It is provided that the first fluid channel section 21, the second fluid channel section 22 and the third fluid channel section 23 are respectively connected to a first valve groove 25 configured in the channel plate 2. It is also provided that the third fluid channel section 23 and the fourth fluid channel section 24 are connected to a second valve groove 26 also configured in the channel plate 2. The fluid channel sections 21 to 24 are respectively configured as holes in the channel plate 2, and the valve grooves 25, 26 are configured as recesses in the channel plate 2.

[0028] Here, the geometry of the valve spools 25, 26 is coordinated with the geometry of the first valve housing 51 of the first valve arrangement 3 and the second valve housing 52 of the second valve arrangement 4. This ensures that when the first valve housing 51 is inserted into the first valve spool 25, a fluidic connection is established between the first valve housing 51 and the associated fluid channel sections 21, 22, 23 of the first valve spool 25, respectively, which fluidic connection is however sealed with respect to the environment of the duct plate 2. It is also ensured that when the second valve housing 52 is inserted into the second valve spool 26, a fluidic connection is established between the second valve housing 52 and the associated fluid channel sections 23 and 24 of the second valve spool 26, respectively, which fluidic connection is also sealed with respect to the environment of the duct plate 2. By way of example, it is provided that the second valve arrangement 4 is arranged symmetrically with respect to the first valve arrangement 3 in the duct plate 2, whereby the metering chamber is defined by the first valve arrangement 3, the second valve arrangement 4 and the third fluid channel section 23 formed between them in the duct plate 2.

[0029] A supply with overpressure and underpressure can be provided for the operation of the metering device 1 . Purely by way of example, this supply is provided by a fluid module 12 , in which, for example, an overpressure pump (not shown) and a underpressure pump (not shown) are accommodated and which has a pressure connection 13 and a underpressure connection 14 .

[0030] The pressure connection 13 is connected to the supply connection 6 of the metering device 1 via a pressure line 15. The vacuum connection 14 is connected to the vacuum connection 8 of the metering device via a vacuum line 16.

[0031] Furthermore, it is necessary to supply electrical energy for the operation of the dosing device 1, which electrical energy can be provided by an energy source (not shown) via an interface 46. It is also preferably provided that control instructions for operating the dosing device can also be provided at the interface 46 by a superior control device (not shown), for example a machine control device of a laboratory automation device. The interface 46 is electrically connected to a communication circuit board 41, which includes a communication component 47, which is designed to preprocess the incoming control instructions. Starting from the communication circuit board 41, the preprocessed control instructions and the provided electrical energy are transmitted to the control circuit board. For this purpose, a cable connection 48 (only schematically shown) is provided between the communication circuit board 41 and the control circuit board 42.

[0032] The control circuit board 42 comprises, purely by way of example, a microprocessor 43, a first high-pressure output stage 44 and a second high-pressure output stage 45, the purpose of which is to implement the electrical control of the valve arrangements 3, 4 and to evaluate the sensor signals of the pressure sensor arrangements 31, 32 described in more detail below.

[0033] The first pressure sensor arrangement 31 includes a first pressure sensor 33 and a second pressure sensor 34, which are respectively assigned to the third fluid channel section 23. By way of example, it is provided that the first pressure sensor 33 has a measuring range that enables accurate detection of not only the negative pressure in the third fluid channel section 23 but also the smaller overpressure in the third fluid channel section 23. It is also provided that the second pressure sensor 34 has a measuring range that enables accurate detection of not only the smaller negative pressure in the third fluid channel section 23 but also the overpressure. Correspondingly, the first pressure sensor 33 and the second pressure sensor 34 have an intersection in terms of their measuring ranges, which intersection can be within the range of normal pressure (1013 mbar), for example. Not only the first pressure sensor 33 but also the second pressure sensor 34 are electrically connected to the control circuit board 42 and provide their sensor signals to the microprocessor 43.

[0034] Second pressure sensor arrangement 32 comprises a third pressure sensor 35 which is associated with fourth fluid channel section 24 and which is likewise electrically connected to control circuit board 42 in order to be able to provide its sensor signal to microprocessor 43 .

[0035] As can be done by the first valve arrangement 3 Figure 1 As can be seen from the schematic diagram in , the first valve housing 51 , which is designed purely by way of example in a rectangular manner, has a first inlet connection 61 , a second inlet connection 62 and a first working connection 63 .

[0036] based on Figure 2The second inlet connection 62 is blocked by the first inlet connection 61 and is provided according to Figure 1 The second valve channel section 65 of the second inlet connection 62 is Figure 2 In the diagram of Figure 2 The sectional plane is arranged so that the first valve channel section 64 associated with the first inlet connection 61 is shown in section. In order to show the course of the second valve channel section 65, the second valve channel section is partially indicated by a dashed line and in Figure 2 Draw it slightly smaller.

[0037] The first valve channel section 64 opens into a valve chamber 67 defined by the first valve housing 51, wherein the opening of the first valve channel section 64 forms a first valve seat 68. The second valve channel section 65 also opens into the valve chamber 67, wherein the opening of the second valve channel section 65 forms a second valve seat 69. The third valve channel section 66 connects the valve chamber 67 to the first working connection 63.

[0038] A strip-shaped piezoelectric bender 70, which is only schematically shown, is arranged in the valve chamber 67 and comprises, by way of example, a carrier layer 73, a first piezoelectric layer 74 and a second piezoelectric layer 75. The first piezoelectric layer 74 is applied to the lower side of the carrier layer 73, while the second piezoelectric layer 75 is applied to the upper side of the carrier layer 73. A first sealing element 71 and a second sealing element 72 are fixed to the lower side of the first piezoelectric layer 74 facing away from the carrier layer 73 in a manner spaced apart from each other. A first compression spring 76 and a second compression spring 77 are arranged on the upper side of the second piezoelectric layer 75 facing away from the carrier layer 73, respectively, in a manner opposite to the first sealing element 71 and the second sealing element 72, and are respectively supported on the inner surface 53 of the valve housing. Furthermore, the piezo bender 70 is received between a first blade-type support 78 and a second blade-type support 79 at the end region facing away from the sealing elements 71 , 72 , which ensures a positionally fixed support of the piezo bender 70 , wherein a shape change of the piezo bender 70 is not hindered.

[0039] The two piezoelectric layers 74, 75 are electrically connected to the control circuit board 42 in a manner not shown in detail, so that a (high voltage) control voltage can be applied to each of the two piezoelectric layers 74, 75. The two piezoelectric layers 74, 75 are designed in such a way that the application of the control voltage causes an expansion of the corresponding piezoelectric layer 74, 75. Since the carrier layer 73 does not expand in this respect, the piezoelectric bender 70 can be optionally transferred to a first bending position (not shown) or a second bending position (not shown). As a result, the piezoelectric bender 70 can realize a valve function, wherein, depending on the corresponding control voltage applied to at least one of the two piezoelectric layers 74, 75, the first sealing element 71 can be optionally lifted from the first valve seat 68 or the second sealing element 73 can be lifted from the second valve seat 69.

[0040] In principle, it can be assumed that there is a predeterminable relationship between the control voltage applied to the respective piezoelectric layer 74, 75 and the bending change of the piezo bender 70, so that the opening cross section for the first valve seat 68 or for the second valve seat 69 can be freely set with the piezo bender 70, and thus a proportional valve function can be achieved by the first valve arrangement 3. Changes in the bending characteristics of the piezo bender 70 that may occur during operation of the first valve arrangement 3 can be compensated by monitoring the pressure in the third fluid channel section 23 by means of the first pressure sensor arrangement 31, by means of a control stored in the microprocessor 43.

[0041] from Figure 1 and Figure 2Thus, it can be seen from the overview that a pressurized fluid or a negative pressure can be optionally provided to the metering chamber by means of the first valve arrangement 3, which forms a supply valve 80 with the first valve seat 68 and the associated first sealing element 71 and a negative pressure valve 81 with the second valve seat 69 and the associated second sealing element 72. For this purpose, an outlet valve 82 is provided by means of a second valve arrangement 4, which is designed identically to the first valve arrangement 3, together with the associated first valve seat 68 and the associated first sealing element 71. Since the two valve arrangements 3 and 4 are fluidically connected to one another purely by way of example, the first working connection 63 of the first valve arrangement 3 is connected to the first working connection 63 of the second valve arrangement 4, which serves as an inlet connection, so that the metering chamber is defined by the first valve housing 51 of the first metering valve 3, the second valve housing 52 of the second metering valve 4 and the third fluid channel section 23 arranged therebetween. The same names and reference numerals are used for the second valve arrangement 4 as for the first valve arrangement 3, even though from a functional point of view the working connection of the second valve arrangement 4 serves as an inlet connection and the first inlet connection 61 of the second valve arrangement 4 forms the working connection. It should also be mentioned that the first valve arrangement 3 serves as a 3 / 3-way proportional valve, while the second valve arrangement 4 serves as a 2 / 22-way proportional valve.

[0042] The following processing method is provided for implementing the metering process: negative pressure is provided at the negative pressure connection 8 of the metering device 1 through the fluid module 12; the second valve seat 69 of the first valve arrangement 3 is temporarily opened by applying a suitable control voltage to the piezoelectric bender 70, thereby lifting the second sealing element 72 from the second valve seat 69 and causing the metering chamber defined by the first valve housing 51, the second valve housing 52 and the third fluid channel section 23 to be loaded with negative pressure; according to the first pressure sensor arrangement 31, a negative pressure is provided to the control circuit board 42. The sensor signal at the microprocessor 43 of the controller is used to adjust the negative pressure loading on the metering chamber; when a predetermined pressure value is reached in the metering chamber, the negative pressure loading on the metering chamber is ended; by applying an appropriate control voltage to the piezoelectric bender 70, the first valve seat 68 of the second valve arrangement 4 is temporarily opened, thereby lifting the first sealing element 71 from the first valve seat 68, and thereby generating a negative pressure loading on the pipette tip 10; when a predetermined pressure value is reached in the metering chamber, the piezoelectric bender for the second valve arrangement 32 is reduced or cut off The control voltage of 70 is used to close the first valve seat 68 of the second valve arrangement 4; an overpressure is provided at the supply connection 6 of the metering device 1 through the fluid module; the first valve seat 68 of the first valve arrangement 3 is temporarily opened by applying an appropriate control voltage to the piezoelectric bender 70, thereby lifting the first sealing element 71 from the first valve seat 69 and causing an overpressure to be applied to the metering chamber; the overpressure to the metering chamber is adjusted according to the sensor signal of the first pressure sensor arrangement 31 provided to the microprocessor 43 of the control circuit board 42. load; end the overpressure loading on the metering chamber when a predetermined pressure value is reached in the metering chamber; temporarily open the first valve seat 68 of the second valve arrangement structure 4 by loading an appropriate control voltage on the piezoelectric bender 70, thereby lifting the first sealing element 71 from the first valve seat 68 and thereby generating an overpressure loading on the pipette tip 10; when a predetermined pressure value is reached in the metering chamber, close the first valve seat 68 of the second valve arrangement structure 4 by reducing or cutting off the control voltage of the piezoelectric bender 70 for the second valve arrangement structure 32.

Claims

1. A dosing device (1) for dosing a liquid, the dosing device comprising: a channel plate (2) in which a fluid channel (11) is formed, the fluid channel extending between a supply connection (6) and an outlet connection (7); a supply valve (80) associated with the supply connection (7); and an outlet valve (82) assigned to the outlet connection (7); and a control device (42) electrically connected to the supply valve (80) and the outlet valve (82), in, A coupling (9) for coupling a pipette tip (10) is assigned to the outlet connection (6), wherein the supply valve (80) and / or the outlet valve (82) are designed as proportional valves.

2. The metering device (1) according to claim 1, characterized in that The fluid channel (11) is connected to a vacuum connection (8) formed on the channel plate (2), and a vacuum valve (81) is assigned to the vacuum connection (8), in particular a proportional valve, which is electrically connected to the control device (42).

3. The dosing device (1) according to claim 1 or 2, characterized in that At least one valve from the group of supply valves (80), outlet valves (82), vacuum valves (81) is designed as a piezo valve, preferably as a piezo bending valve, in particular as a 3 / 3-way piezo bending valve.

4. The metering device (1) according to claim 2 or 3, characterized in that The supply valve (80) and the negative pressure valve (81) are received together in a first valve housing (51), which has a first inlet connection (61) connected to the supply connection (6), and a second inlet connection (62) connected to the negative pressure connection (8), and a first working connection (63) connected to the outlet valve (82) is constructed on the first valve housing (51).

5. The metering device (1) according to claim 4, characterized in that The outlet valve (82) is received in a second valve housing (52), which has a second inlet connection (63) connected to the first working connection (63) of the first valve housing (51), and has a second working connection (62) connected to the outlet connection (7).

6. The metering device (1) according to claim 5, characterized in that The fluid channel (11) has a first valve groove (25) configured to receive the first valve housing (51) and a second valve groove (26) configured to receive the second valve housing (52).

7. The metering device (1) according to claim 6, characterized in that The maximum metering volume is determined by the first valve housing (51), the second valve housing (52) and a fluid channel section (23) extending between the first valve housing (51) and the second valve housing (52), and the volume share of the fluid channel section (23) in the maximum metering volume is less than 20 percent, preferably less than 10 percent.

8. The metering device (1) according to claim 6 or 7, characterized in that A first pressure sensor arrangement (31) is arranged between the first valve groove (25) and the second valve groove (26), and the first pressure sensor arrangement is electrically connected to the control device (42), and a second pressure sensor arrangement (32) is allocated to the outlet connector (7), and the second pressure sensor arrangement is electrically connected to the control device (42).

9. The metering device (1) according to claim 8, characterized in that The first pressure sensor arrangement (31) comprises a first pressure sensor (33) having a first measuring range and a second pressure sensor (34) having a second measuring range, wherein the first measuring range and the second measuring range have an intersection.

10. The dosing device (1) according to any one of the preceding claims, characterized in that A delivery pump, in particular designed as a diaphragm pump, is assigned to the supply connection (6) and / or a vacuum pump, in particular designed as a diaphragm pump, is assigned to the vacuum connection (7).

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