Dosing device for dosing liquids

Abstract

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

Description

[0001] The invention relates to a dosing device for dosing liquids.

[0002] DE 10 2020 205 073 A1 discloses a metering device for metering liquids, comprising a fluid unit for selectively providing an overpressure and a negative pressure to a working gas accommodated in a fluid channel, which is connected to the fluid unit at a first end region and which comprises a second end region designed to receive and discharge a predeterminable volume of liquid, comprising a first valve device and a second valve device, which are arranged spaced apart from one another along the fluid channel and are each designed to selectively block or release the fluid channel in order to form a fluid reservoir in the fluid channel, delimited by the two valve devices and intended for storing working gas, comprising a control device for controlling the valve devices, wherein a pressure sensor is assigned to the fluid reservoir,which is designed to provide a pressure signal as a function of a working gas pressure and is electrically connected to the control device.

[0003] US 2019 / 0 321 815 A1 discloses a method for controlling the aspiration and / or dispensing of a liquid dose or the generation of a liquid dose in a pipette or in a container, the method comprising the following steps: first, loading a first pipette with a first working medium at a first pressure with a first sign with respect to a reference pressure, whereby the liquid dose is dispensed into the container or the liquid dose is sucked into the first pipette, second, loading a second pipette with a second working medium at a second pressure with a second sign with respect to the reference pressure, whereby the liquid dose is dispensed into the vessel or the liquid dose is sucked into the second pipette, releasing a pressure in the first working medium through a controlled valve arrangement to the reference pressure between the first and the second loading.

[0004] US 2013 / 0 108 521 A1 discloses a dispensing device for sucking a dispensing liquid in an amount corresponding to multiple dispenses from a dispensing port of a nozzle unit having a flow passage filled with a pressure transmission medium, with a gap located between the pressure transmission medium and the dispensing liquid, and for continuously dispensing very small amounts of liquid droplets, the dispensing device comprising: a nozzle unit, the nozzle unit having a flow passage communicating with the dispensing port; a storage unit having a liquid regulating device and configured to supply the pressure transmission medium in a liquid phase under a regulated pressure to the nozzle unit side; a pressurizing unit having means for supplying a pressurized gas under a regulated pressure to the storage unit side;a pump mechanism fluidly communicating with the storage unit and the nozzle unit; a branch unit provided with a branch flow passage for connecting the nozzle unit and the storage unit to each other; a discharge valve having means for establishing or blocking communication between the branch unit and the nozzle unit; a supply valve having means for establishing or blocking communication between the branch unit and the storage unit;and a control unit, wherein the control unit is configured to perform control such that, in a state where the discharge valve is closed and the supply valve is opened, the pressurized gas is supplied to the storage unit side at a pressure regulated by the pressurizing unit, and the pressure transmission medium in a liquid phase is supplied to the supply valve side at a certain pressure regulated by the storage unit, and that the discharge valve is then opened and closed at predetermined timings to thereby continuously discharge the very small amounts of liquid droplets in a flying manner.

[0005] US 2002 / 0 011 276 A1 discloses a gas cushion microdosing system for dosing liquid volumes in the microliter and submicroliter range, comprising a liquid reservoir with a storage space for the liquid to be dosed, the boundary of which is penetrated by an outwardly leading liquid passage and a gas passage, a gas displacement system connected to the gas passage with a micropump for pumping a gas, a gas reservoir connected to the micropump,a connection of the gas reservoir to the gas passage and valve devices for opening or closing the connection of the gas reservoir to the gas passage and a dosing control operatively connected to the micropump and the valve devices for closing the valve devices and generating a negative pressure or positive pressure in the gas reservoir by actuating the micropump and for applying the negative pressure or positive pressure from the gas reservoir to the liquid reservoir by actuating the valve devices in order to absorb liquid into the storage space through the liquid passage or to discharge it from the storage space.

[0006] The object of the invention is to provide a dosing device with which a higher dosing precision can be achieved.

[0007] This object is achieved for a dosing device of the type mentioned at the outset according to the following features: Dosing device for dosing liquids, with a channel plate in which a fluid channel is formed which extends between a supply connection and an output connection, with a supply valve assigned to the supply connection and with an output valve assigned to the output connection, and with a control device which is electrically connected to the supply valve and the output valve, wherein a coupling for coupling a pipetting tip is assigned to the output connection and wherein the supply valve and / or the output valve is designed as a proportional valve.

[0008] The channel plate, which can also be referred to as the base body, is penetrated by a fluid channel designed for fluid communication between the supply port and the output port. For example, a fluid module, particularly designed as a combination of a fluid source and a fluid sink, can be connected to the supply port. With the aid of this module, a pressurized fluid and a negative pressure can be supplied to the fluid channel, as required. For example, the channel plate is designed as a single piece or in multiple parts, particularly as a plastic injection-molded part.

[0009] A coupling designed for coupling a pipette tip is assigned to the output port. A pipette tip is a tube section, preferably made of a plastic material, in particular with a conical shape, which is intended to temporarily hold a liquid. Such pipette tips are used particularly in laboratory technology for dosing liquids. The coupling assigned to the output port for coupling the pipette tip is designed for fluid-tight reception of the pipette tip, so that neither a pressurized fluid nor a liquid held in the pipette tip can escape between the coupling and the pipette tip.

[0010] The function of the supply valve, which is assigned to the supply connection, is to selectively open or close a fluidically communicating connection between the fluid module, which can be connected to the supply connection, and a section of the fluid channel extending between the supply valve and the outlet valve. This gives the supply valve the task of enabling or blocking a corresponding overpressure or a corresponding negative pressure in the fluid channel, depending on the overpressure or negative pressure provided by the fluid module at the supply connection.

[0011] The function of the outlet valve associated with the outlet connection is to selectively open or close a fluidically communicating connection between the section of the fluid channel extending between the supply connection and the outlet valve, and the outlet connection with the associated coupling. The outlet valve thus has the function of selectively enabling or blocking pressure equalization between the environment of the dosing device and the fluid channel. During this pressure equalization, a liquid can also be sucked into or discharged from the pipette tip, which can be attached to the coupling.

[0012] Here, at least one valve from the group: supply valve, output valve, is designed as a proportional valve, wherein the proportional valve can provide a predeterminable valve opening depending on an electrical control signal provided by the control device. The proportional valve can be continuously adjusted between a fully closed functional state and a fully open functional state. Preferably, there is a proportional relationship between the control signal, which is in particular an electrical control voltage or an electrical control current that can be predetermined by the control device, and the functional state of the proportional valve.However, depending on the design of the proportional valve and an actuator associated with the proportional valve, which is responsible for converting the electrical energy provided by the control device into a mechanical movement, there may be a non-proportional relationship between the control signal and the functional state of the proportional valve instead of the proportional relationship.

[0013] The control device is embodied, for example, as a microprocessor or microcontroller and is designed to execute a stored computer program. Preferably, the control device is connected to a higher-level controller, which is designed to provide control commands to the control device in order to effect a suitable change in the functional states of the supply valve and the outlet valve. This higher-level controller can be, for example, a machine controller of a laboratory automation device, which, for example, has a receiving surface for a plurality of sample containers and a manipulator for a 1-dimensional, 2-dimensional, or 3-dimensional relative movement of the dosing device relative to the sample containers.Alternatively, the control device can be connected to a switching device, in particular fixed to the channel plate, which can be operated by an operator in order to be able to provide switching commands for the supply valve and the outlet valve directly to the control device.

[0014] Advantageous further developments of the invention are the subject of the subclaims.

[0015] It is expedient if the fluid channel is connected to a vacuum connection formed on the channel plate, and that a vacuum valve, in particular designed as a proportional valve, is assigned to the vacuum connection and is electrically connected to the control device. With the additional vacuum connection, instead of a fluid module which is designed to provide either overpressure or underpressure at the supply connection, a fluid source intended exclusively for providing overpressure can be connected to the supply connection, while a fluid sink intended exclusively for providing underpressure is connected to the vacuum connection. This allows for faster provision of overpressure or underpressure into the fluid channel of the channel plate due to shorter fluid paths.This results in the dosing device being able to switch more quickly, for example, between a suction process for a liquid into the pipette tip and a dispensing process of the liquid from the pipette tip. Preferably, the vacuum valve is designed as a proportional valve so that, similar to the supply valve and / or the outlet valve, it can be continuously adjusted by the control device between a fully closed state and a fully open state.

[0016] Preferably, at least one valve from the group consisting of supply valve, outlet valve, and vacuum valve is designed as a piezoelectric valve, preferably as a piezoelectric bending valve, in particular as a 3 / 3-way piezoelectric bending valve. By using piezoelectric valves comprising at least one actuator made of a piezoelectric material, a compact design for the respective valve can be achieved. Furthermore, compared to a solenoid valve, a piezoelectric valve generates significantly less heat because it is operated with a high voltage (in particular greater than 300 V) but a low current. This means that heating of the dosing device, the pipette tip connected to it, and the liquid contained in the pipette tip can be kept at a comparatively low level.

[0017] In an advantageous embodiment of a piezo valve, the piezoelectric actuator is strip-shaped and applied to a likewise strip-shaped carrier material, in particular a spring steel. By applying a suitable control voltage to the piezoelectric actuator, the curvature of the composite, also referred to as a piezo bender, consisting of the piezoelectric actuator and carrier material can be influenced. This allows, for example, a sealing element attached to the piezo bender to be selectively placed on a valve seat formed in the fluid channel in a sealing manner or to be lifted off this valve seat. It is particularly advantageous if such a piezo bender can be curved in opposite directions by a suitable arrangement of several piezoelectric layers on the carrier material and has several sealing elements, whereby a 3 / 3-way valve function can be realized.Such a proportional valve has, for example, a first input port, a second input port and a working port, wherein, depending on an electrical control of the piezo bender, a fluidically communicating connection between the first input port and the working port or between the second input port and the working port can be closed or released as desired.

[0018] Such a 3 / 3-way piezo valve can be used for a dosing device in that the supply valve and the vacuum valve are jointly housed in a first valve housing. The first valve housing has a first input port connected to the supply port and a second input port connected to the vacuum port. A first working port connected to the output valve is formed on the first valve housing. Provided that a fluid source is connected to the supply port and a fluid sink is connected to the vacuum port, such a 3 / 3-way piezo valve can provide a freely selectable and quickly switchable pressurization or vacuum application at the working port.

[0019] 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 valves of the metering device are implemented as identical parts. In the outlet valve, however, only the second inlet connection and the working connection are used, while the first inlet connection remains unused. Accordingly, the outlet valve is operated only as a 2 / 2-way piezo valve.

[0020] In a further embodiment of the invention, it is provided that the fluid channel has a first valve shaft which is designed to receive the first valve housing, and a second valve shaft which is designed to receive the second valve housing. The first valve shaft and the second valve shaft are introduced as recesses in the channel plate. It is preferably provided that a section of the fluid channel extending from the supply connection and a section of the fluid channel extending from the vacuum connection open into the first valve shaft. Furthermore, it is provided that a further section of the fluid channel extends between the first valve shaft and the second valve shaft, which opens into the two valve shafts. In addition, it is provided that a section of the fluid channel connected to the output connection extends from the second valve shaft.The first valve shaft and the second valve shaft are designed such that the first valve housing and the second valve housing, with their respective input ports and working ports, are fluidically connected to the respective sections of the fluid channel. Preferably, the first valve shaft and the second valve shaft are designed such that, upon insertion of the first valve housing and the second valve housing, fluid-tight connections are created between the input ports and the associated sections of the fluid channel, as well as between the working ports and the associated sections of the fluid channel, also with respect to the environment.

[0021] It is preferably provided that a maximum dosing volume is determined by the first valve housing, the second valve housing and a fluid channel section extending between the first valve housing and the second valve housing, and that a volume fraction of the fluid channel section in the maximum dosing volume is less than 20 percent, preferably less than 10 percent. In particular, it is provided that the maximum dosing 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 optionally by a section of the fluid channel extending between the second valve housing and the outlet connection. The volume fraction of the fluid channel section in this maximum dosing volume is less than 20 percent, in particular less than 10 percent.Since the valve housings have to be manufactured with a high degree of precision for the respective valves to function properly, it is advantageous for the definition of the maximum dosing volume if the maximum dosing volume is predominantly determined by the valve housings, so that somewhat lower requirements can be placed on the precision of the fluid channel section.

[0022] It is expedient if a first pressure sensor arrangement is arranged between the first valve shaft and the second valve shaft, which is electrically connected to the control device, and that a second pressure sensor arrangement is assigned to the output connection, which is electrically connected to the control device. The first pressure sensor arrangement serves to determine the pressure in the dispensing volume, which is determined by the first valve housing, the second valve housing and the fluid channel section in between, wherein a suction process or a dispensing process for liquid into the pipette tip or from the pipette tip is significantly determined by the pressure prevailing in the dispensing volume. The second pressure sensor arrangement serves to determine the pressure actually present at the pipette tip in order to be able to carry out particularly advantageous control for the dispensing process.

[0023] In a further embodiment of the invention, 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 two pressure sensors with different measuring ranges for the first pressure sensor arrangement, an advantageous improvement in 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 level of precision in the negative pressure range and the second pressure sensor can have a high level of precision in the positive pressure range. The measuring ranges of the two pressure sensors are selected such that they overlap.

[0024] This also allows the control device, which is electrically connected to the two pressure sensors, to check the function of the two pressure sensors by comparing the sensor signals in the pressure range in which the two measuring ranges overlap.

[0025] In an advantageous development of the invention, it is provided that a feed pump, in particular designed as a diaphragm pump, is assigned to the supply connection and / or that a vacuum pump, in particular designed as a diaphragm pump, is assigned to the vacuum connection.

[0026] An advantageous embodiment of the invention is illustrated in the drawing. Herein: Fig. 1 a strictly schematic overview of a dosing device with a channel plate, valve arrangements accommodated therein and a control device, and Fig. 2 a strictly schematic sectional view of a valve arrangement with a piezo bender accommodated therein.

[0027] A schematic in the Fig. The dosing device 1 shown in Figure 1 is designed for use in laboratory automation and is used to dose liquid samples and reagents. For example, the dosing device 1 can be mounted on a manipulator (not shown) of a laboratory automation device, so that the dosing device 1 can be moved, for example, over a surface on which sample containers (not shown) are arranged, in order to take up liquid from the sample containers or to discharge it into the sample containers.

[0028] The dosing device 1 has a channel plate 2, which can also be considered the base body of the dosing device 1 and which can optionally be accommodated in a housing (not shown). A first valve arrangement 3, a second valve arrangement 4, and a control device 5 are assigned to the channel plate 2. Furthermore, the channel plate 2 has a supply connection 6, an output connection 7, and a vacuum connection 8. Attached to the output connection 7 is a coupling 9 (shown only schematically), to which a pipette tip 10 is coupled.

[0029] The channel plate 2 is penetrated by a fluid channel 11, which is defined 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. Here, it is provided that the first fluid channel section 21, the second fluid channel section 22 and the third fluid channel section 23 are each connected to a first valve shaft 25, which is formed in the channel plate 2. Furthermore, it is provided that the third fluid channel section 23 and that for the fluid channel section 24 are connected to a second valve shaft 26, which is also formed in the channel plate 2. For example, the fluid channel sections 21 to 24 are each formed as bores in the channel plate 2, while the valve shafts 25, 26 are formed as depressions in the channel plate 2.

[0030] The geometries of the valve shafts 25, 26 are matched to the geometry of a first valve housing 51 of the first valve arrangement 3 and of a 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 shaft 25, fluidically communicating connections are established between the first valve housing 51 and the associated fluid channel sections 21, 22, 23 of the first valve shaft 25, which are, however, sealed off from the environment of the channel plate 2. Furthermore, it is ensured that when the second valve housing 52 is inserted into the second valve shaft 26, fluidically communicating connections are established between the second valve housing 52 and the associated fluid channel sections 23 and 24 of the second valve shaft 26, which are likewise sealed off from the environment of the channel plate 2.By way of example, it is provided that the second valve arrangement 4 is arranged in the channel plate 2 in a mirror image to the first valve arrangement 3, whereby a metering chamber is determined by the first valve arrangement 3, the second valve arrangement 4 and the third fluid channel section 23 formed therebetween in the channel plate 2.

[0031] For operation of the dosing device 1, a supply of positive pressure and negative pressure must be provided. Purely by way of example, this supply is provided by a fluid module 12, which, for example, accommodates a positive pressure pump (not shown) and a negative pressure pump (not shown) and has a pressure connection 13 and a negative pressure connection 14.

[0032] The pressure connection 13 is connected to the supply connection 6 of the dosing device 1 via a pressure line 15. The vacuum connection 14 is connected to the vacuum connection 8 of the dosing device via a vacuum line 16.

[0033] Furthermore, the operation of the dosing device 1 requires a supply of electrical energy, which can be provided via an interface 46 from a power source (not shown). Furthermore, it is preferably provided that control commands for operating the dosing device can also be provided at the interface 46 from a higher-level control device (not shown), for example a machine control system of a laboratory automation device. The interface 46 is electrically connected to a communications board 41, which includes a communications module 47 designed to process incoming control commands. From the communications board 41, the processed control commands and the provided electrical energy are forwarded to a control board.For this purpose, a cable connection 48, shown only schematically, is provided between the communication board 41 and the control board 42.

[0034] The task of the control board 42, which purely by way of example comprises a microprocessor 43, a first high-voltage output stage 44 and a second high-voltage output stage 45, is to carry out an electrical control of the valve arrangements 3, 4 and an evaluation of sensor signals of the pressure sensor arrangements 31, 32 described in more detail below.

[0035] The first pressure sensor arrangement 31 comprises a first pressure sensor 33 and a second pressure sensor 34, each of which is assigned to the third fluid channel section 23. For example, the first pressure sensor 33 may have a measuring range that enables both precise detection of a negative pressure in the third fluid channel section 23 and a slight positive pressure in the third fluid channel section 23. Furthermore, the second pressure sensor 34 may have a measuring range that enables both precise detection of a slight negative pressure and an positive pressure in the third fluid channel section 23. Accordingly, the first pressure sensor 33 and the second pressure sensor 34 have an intersection in terms of their measuring ranges, which may be located, for example, in the range of normal pressure (1013 mbar).Both the first pressure sensor 33 and the second pressure sensor 34 are electrically connected to the control board 42 and provide their sensor signals to the microprocessor 43.

[0036] The second pressure sensor arrangement 32 comprises a third pressure sensor 35, which is assigned to the fourth fluid channel section 24 and which is also electrically connected to the control board 42 in order to be able to provide its sensor signals to the microprocessor 43.

[0037] As can be seen from the schematic representation of the first valve arrangement 3 in the Fig. 1, the purely exemplary cuboid-shaped first valve housing 51 has a first inlet connection 61, a second inlet connection 62 and a first working connection 63.

[0038] Due to the sectional view of the Fig. 2, the second input terminal 62 is covered by the first input terminal 61 and a second input terminal 62 is connected to the first input terminal 61 according to the Fig. 1 associated second valve channel section 65 runs in the illustration of the Fig. 2 behind the cutting plane of the Fig. 2, which is arranged in such a way that a first valve channel section 64 associated with the first input connection 61 is shown in section. In order to illustrate the course of the second valve channel section 65, this is partially dashed and slightly smaller in the Fig. 2 is shown.

[0039] The first valve channel section 64 opens into a valve chamber 67 defined by the first valve housing 51, with an opening of the first valve channel section 64 forming a first valve seat 68. The second valve channel section 65 also opens into the valve chamber 67, with an opening of the second valve channel section 65 forming a second valve seat 69. A third valve channel section 66 connects the valve chamber 67 to the first working connection 63.

[0040] Arranged in the valve chamber 67 is a strip-shaped piezo bender 70, shown only schematically, which, for example, has a carrier layer 73, a first piezoelectric layer 74, and a second piezoelectric layer 75. The first piezoelectric layer 74 is applied to an underside of the carrier layer 73, while the second piezoelectric layer 75 is applied to an upper side of the carrier layer 73. A first sealing element 71 and a second sealing element 72 are fixed at a distance from one another on an underside of the first piezoelectric layer 74, which faces away from the carrier layer 73. Arranged on an upper side of the second piezoelectric layer 75, which faces away from the carrier layer 73, opposite the first sealing element 71 and the second sealing element 72, respectively, are a first compression spring 76 and a second compression spring 77, each of which is supported on an inner surface 53 of the valve housing.Furthermore, the piezo bender 70 is accommodated at an end region facing away from the sealing elements 71, 72 between a first cutting edge bearing 78 and a second cutting edge bearing 79, which ensure a stationary mounting of the piezo bender 70, wherein a change in shape of the piezo bender 70 is not hindered.

[0041] The two piezoelectric layers 74, 75 are electrically connected to the control 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. For example, the two piezoelectric layers 74, 75 are designed such that applying a control voltage leads to an expansion of the respective piezoelectric layer 74, 75. Since the carrier layer 73, in contrast, does not expand, the piezo bender 70 can thus be transferred selectively into a first curvature position (not shown) or a second curvature position (not shown).Thus, the piezo bender 70 can be used for a valve function in which, depending on the respective control voltage applied to at least one of the two piezoelectric layers 74, 75, either the first sealing element 71 is lifted from the first valve seat 68 or the second sealing element 73 is lifted from the second valve seat 69.

[0042] In principle, it can be assumed that a predeterminable relationship exists between a control voltage applied to the respective piezoelectric layer 74, 75 and a change in the curvature of the piezo bender 70, so that an opening cross-section for the first valve seat 68 or for the second valve seat 69 can be freely adjusted with the piezo bender 70, thus implementing a proportional valve function through the first valve arrangement 3. Any changes in the curvature behavior of the piezo bender 70 that may occur during operation of the first valve arrangement 3 can be compensated for by monitoring the pressure in the third fluid channel section 23 by means of the first pressure sensor arrangement 31 through a control system stored in the microprocessor 43.

[0043] From the overview of the Fig. 1 and Fig.2 thus shows that with the aid 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 vacuum valve 81 with the second valve seat 69 and the associated second sealing element 72, a pressurized fluid or a vacuum can be selectively supplied to the metering chamber. For this purpose, an outlet valve 82 is provided with the aid of the second valve arrangement 4, which is structurally identical to the first valve arrangement 3, with the associated first valve seat 68 and the associated first sealing element 71.Since the two valve assemblies 3 and 4 are fluidically interconnected in a mirror-inverted manner purely by way of example, so that the first working port 63 of the first valve assembly 3 is connected to the first working port 63 of the second valve assembly 4, which is used as the input port, 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 designations and reference symbols are used for the second valve assembly 4 as for the first valve assembly 3, although from a functional point of view the working port of the second valve assembly 4 is used as the input port and the first input port 61 of the second valve assembly 4 forms a working port.It should also be mentioned that the first valve arrangement 3 is used as a 3 / 3-way proportional valve, while the second valve arrangement 4 is used as a 2 / 2-way proportional valve.

[0044] The following procedure is provided for carrying out a dosing process: Providing a negative pressure by the fluid module 12 at the negative pressure connection 8 of the dosing device 1; temporarily opening the second valve seat 69 of the first valve arrangement 3 by applying a suitable control voltage to the piezo bender 70, whereby the second sealing element 72 is lifted from the second valve seat 69 and a negative pressure is applied to the dosing chamber, which is delimited by the first valve housing 51, the second valve housing 52 and the third fluid channel section 23; regulating the negative pressure application to the dosing chamber based on sensor signals from the first pressure sensor arrangement 31, which are provided to the microprocessor 43 of the control board 42; terminating the negative pressure application to the dosing chamber when a predetermined pressure value is reached in the dosing chamber;temporarily opening the first valve seat 68 of the second valve arrangement 4 by applying a suitable control voltage to the piezo bender 70, whereby the first sealing element 71 is lifted from the first valve seat 68 and resulting in a negative pressure being applied to the pipette tip 10; closing the first valve seat 68 of the second valve arrangement 4 by reducing or switching off the control voltage for the piezo bender 70 of the second valve arrangement 32 when a predetermined pressure value is reached in the dosing chamber; providing an overpressure through the fluid module at the supply connection 6 of the dosing device 1; temporarily opening the first valve seat 68 of the first valve arrangement 3 by applying a suitable control voltage to the piezo bender 70, whereby the first sealing element 71 is lifted from the first valve seat 69 and an overpressure being applied to the dosing chamber;Control of the overpressurization of the dosing chamber based on sensor signals from the first pressure sensor arrangement 31, which are provided to the microprocessor 43 of the control board 42; Terminating the overpressurization of the dosing chamber when a predetermined pressure value is reached in the dosing chamber; Temporarily opening the first valve seat 68 of the second valve arrangement 4 by applying a suitable control voltage to the piezo bender 70, whereby the first sealing element 71 is lifted from the first valve seat 68 and resulting in overpressurization of the pipette tip 10; Closing the first valve seat 68 of the second valve arrangement 4 by reducing or switching off the control voltage for the piezo bender 70 of the second valve arrangement 32 when a predetermined pressure value is reached in the dosing chamber.

Claims

[1] Dosing device (1) for dosing liquids, with a channel plate (2) in which a fluid channel (11) is formed, which extends between a supply connection (6) and an output connection (7), with a supply valve (80) assigned to the supply connection (7) and with an output valve (82) assigned to the output connection (7), and with a control device (42) which is electrically connected to the supply valve (80) and the output valve (82), wherein a coupling (9) for coupling a pipetting tip (10) is assigned to the output connection (6), and wherein the supply valve (80) and / or the output valve (82) is designed as a proportional valve. [2] Dosing device (1) according to claim 1, characterized bythat the fluid channel (11) is connected to a vacuum connection (8) formed on the channel plate (2), and that the vacuum connection (8) is assigned a vacuum valve (81), designed in particular as a proportional valve, which is electrically connected to the control device (42). [3] Dosing device (1) according to claim 1 or 2, characterized by that at least one valve from the group: supply valve (80), outlet valve (82), vacuum valve (81), is designed as a piezo valve, preferably as a piezo bending valve, in particular as a 3 / 3-way piezo bending valve. [4] Dosing device (1) according to claim 2 or 3, characterized bythat the supply valve (80) and the vacuum valve (81) are accommodated together in a first valve housing (51) which has a first inlet connection (61) which is connected to the supply connection (6) and which has a second inlet connection (62) which is connected to the vacuum connection (8) and that a first working connection (63) which is connected to the outlet valve (82) is formed on the first valve housing (51). [5] Dosing device (1) according to claim 4, characterized by that the output valve (82) is accommodated in a second valve housing (52) which has a second input port (63) which is connected to the first working port (63) of the first valve housing (51) and which has a second working port (62) which is connected to the output port (7). [6] Dosing device (1) according to claim 5, characterized bythat the fluid channel (11) has a first valve shaft (25) which is designed to receive the first valve housing (51), and a second valve shaft (26) which is designed to receive the second valve housing (52). [7] Dosing device (1) according to claim 6, characterized by that a maximum dosing 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 that a volume fraction of the fluid channel section (23) in the maximum dosing volume is less than 20 percent, preferably less than 10 percent. [8] Dosing device (1) according to claim 6 or 7, characterized bythat a first pressure sensor arrangement (31) is arranged between the first valve shaft (25) and the second valve shaft (26), which is electrically connected to the control device (42), and that a second pressure sensor arrangement (32) is assigned to the output connection (7), which is electrically connected to the control device (42). [9] Dosing device (1) according to claim 8, characterized by that the first pressure sensor arrangement (31) comprises a first pressure sensor (33) with a first measuring range and a second pressure sensor (34) with a second measuring range, wherein the first measuring range and the second measuring range have an intersection. [10] Dosing device (1) according to one of the preceding claims, characterized bythat a feed pump, in particular designed as a diaphragm pump, is assigned to the supply connection (6) and / or that a vacuum pump, in particular designed as a diaphragm pump, is assigned to the vacuum connection (7).

Images