Pipetting aid with continuous operation

Abstract

A pipetting device (11) for receiving a pipette is shown and described, wherein the pipette is intended for aspiration and dispensing of a liquid. The pipetting device (11) comprises a receiving device (15) for a pipette, a pump (121) with continuously adjustable pumping capacity, and at least one valve for controlling the pumping direction such that, during operation, the pump (121) generates an overpressure or a vacuum in the receiving device (15) depending on the position of the valve. Furthermore, the pipetting device (11) comprises at least one actuation button (14a) for switching on the pump (121) and for controlling the valve.The pipetting device (11) is characterized in that the pipetting device has a sensor arrangement (139, 141, 143, 153) for detecting a gas flow in the line, wherein a pumping power of the pump is continuously controlled by an actuation key signal generated by variable key pressure of the actuation key and the detection of the gas flow.

Description

TECHNICAL AREA OF INVENTION

[0001] The invention relates to a pipetting aid according to the preamble of claim 1. BACKGROUND OF THE INVENTION

[0002] A pipetting aid is a laboratory device that simplifies the dispensing of liquid using a pipette. The pipette has an upper and a lower opening. During pipetting, a specific amount of liquid is first aspirated and then dispensed, either as a whole or in smaller doses. The flow rate through the lower opening of the pipette is controlled by the volume of air flowing through its upper opening. The volume drawn out of the upper opening of the pipette must be supplied through its lower opening, and vice versa. This applies when air is drawn in or dispensed. However, when moving a liquid, such as water, the volume of air, in order to precisely correspond to a specific aspirated or dispensed volume of liquid, is subject to various physical laws that influence the volume (temperature, pressure, density of the liquid, etc.).

[0003] When using a pipetting aid, it is connected to the top opening of the pipette. The pipetting aid determines the flow rate at the top opening and thus also controls the flow rate at the bottom opening. This applies to both liquid aspiration and liquid dispensing. Motorized pipetting aids have a pump, which is usually activated by pressing a button on the pipetting aid. The pump creates a vacuum when liquid is to be aspirated, i.e., when the pipette is to be filled with a specific volume. During aspiration, air is drawn in through the top opening of the pipette, so that liquid flows into the pipette when the pipette tip is immersed in the liquid. The pump can also be used to create positive pressure in the connecting line during dispensing.

[0004] A diaphragm pump is typically used. It is designed to deliver a predetermined mechanical pumping power and optionally allows this power to be changed via an adjustment device.

[0005] Apart from the use of an adjustment device, the pump thus has only two operating states: "Off" or "Pump." A simple on / off switch can be used for this. One disadvantage of using such a pump is that the pipetting aid has a minimum pumping capacity that cannot be undercut. This means that during aspiration, the flow rate cannot increase continuously from zero without the use of needle valves or similar mechanical flow regulators, but instead jumps to a minimum flow rate immediately after the pump starts. This is referred to as a stepped pump. To enable stepless operation of such a pump, it is known to combine the stepped pump with a continuously variable valve. However, this is complex because additional mechanical components are required, which also need to be controlled. TASK

[0006] It is therefore an object of the present invention to provide an improved pipetting aid that enables smooth and thus stepless aspiration and dispensing without the need for a stepless valve. A further object of the invention is to provide a pipetting aid that allows the user to dispense a user-defined volume precisely and repetitively, thus enabling the user to perform faster, easier, and more precise repetitive dispensing of liquid. Another object of the invention is to prevent overfilling of a pipette, given its known volume, in order to avoid damage to the device or the need for time-consuming cleaning of the pipetting aid. DESCRIPTION

[0007] The problem is solved in a pipetting aid by the features listed in the characterizing section of claim 1. Further developments and / or advantageous embodiments are the subject of the dependent claims.

[0008] The invention relates to a pipetting aid for holding a pipette, wherein the pipette is intended for the aspiration and dispensing of a liquid. The pipetting aid comprises a receiving device for holding a pipette, a pump with a continuously variable operating curve, and at least one valve for controlling the pump direction such that, during operation, the pump generates either positive or negative pressure in the pipetting aid depending on the position of the valve. Furthermore, the pipetting aid includes a line between the receiving device and the pump, and at least one actuation button for operating the pump and controlling the valve.For example, the actuation button, in conjunction with a sensor, is designed to generate an actuation button signal that can assume a variety of values ​​between zero and a certain maximum level, with the control unit controlling the pump's pumping power depending on the respective assumed value of the actuation button signal.

[0009] Pressing the activation button activates the pump and opens or closes the valve. The pump output is continuously adjustable by varying the pressure applied to the button. The valve sets the pump's direction of flow. This direction determines whether the pump creates positive or negative pressure in the pipetting aid. The negative or positive pressure generated by the pump is transmitted via the line to the receiving device and a pipette held within it. The resulting pressure difference between the top and bottom of the pipette causes liquid to be drawn into or dispensed from the pipette. Negative pressure draws liquid in, while positive pressure dispenses liquid from the pipette.It goes without saying that during aspiration the front end of the pipette must be immersed in the liquid to be aspirated, and that during dispensing the pipette tip is placed over a container that is intended to hold a certain amount of the dispensed liquid.

[0010] For example, the actuation button is connected to a pressure-sensitive sensor, and the actuation button signal changes with the pressure applied. This is a simple arrangement that can be implemented, for instance, using a strain gauge. The advantage of using a strain gauge is that its electrical resistance changes proportionally to the mechanical strain applied to it. This change in resistance can be measured with a Wheatstone bridge circuit, which is typically supplied with a constant direct current (DC) voltage. Accordingly, the output signal of a strain gauge is primarily a DC signal whose level or voltage changes with the mechanical load.

[0011] For example, the actuation button is movable and, in conjunction with the sensor, generates an actuation signal whose value varies depending on the button stroke or movement path. The button stroke, in conjunction with a spring, can exert a variable force on a pressure-sensitive sensor, such as a strain gauge.

[0012] According to a preferred embodiment of the invention, the actuation button signal is an analog signal, e.g., generated by a pressure-sensitive sensor, and the pump's output is coupled to the level of the analog signal. The greater the actuation button's travel, the higher the level of the analog signal. The analog signal, in turn, is transmitted directly or indirectly to the pump via a processor integrated into the pipetting aid.

[0013] The actuation button is advantageously pre-tensioned to its rest position by a compression spring. This has the benefit of providing the user with haptic feedback through progressive resistance. With a spring-loaded actuation button, the user feels a change in resistance, providing a direct sense of interaction.

[0014] According to a preferred embodiment of the invention, the compression spring is supported on a bending tab. This tab can be part of a printed circuit board. The bending tab can be manufactured by cutting a U-shaped tab or tongue out of the printed circuit board. The strain gauge is applied to the printed circuit board where the bending tab bends, for example by means of a soldered or adhesive bond.

[0015] The pipetting device has a sensor arrangement configured to detect a gas flow in the line, wherein the pipetting device is further configured to continuously control a pumping power of the pump by means of an actuation key signal generated by variable key pressure of the actuation key and the detection of the gas flow.

[0016] In one embodiment, the line between the receiving device and the pump is connected to a bypass line, and the sensor arrangement is configured to detect the gas flow in the line by detecting a gas flow in the bypass line. For example, a gas flow in the bypass line is coupled to the level of the (e.g., analog) actuation button signal.

[0017] The bypass line is an additional path that is decoupled from the main line and coupled back into the main line downstream, e.g. a narrower one.

[0018] In one embodiment, the pipetting aid has a gas flow sensor in the line between the receiving device and the pump, and the mass or volume flow in this line is coupled to the level of the actuation button signal via the control unit. This has the advantage that the pump output can be continuously controlled by varying the button pressure and depending on the measured mass or volume flow in the line. The mass or volume flow can be displayed on a screen, for example, as a bar graph whose size changes depending on the mass or volume flow.

[0019] In one embodiment, the sensor arrangement is based on a differential pressure principle, wherein a portion of the gas is routed through the bypass and the gas flow in the bypass is detected or measured using a thermal measuring principle. In the thermal measuring principle, two temperature sensors detect the temperature difference before and after a heated element. The detection of the gas flow is then based on the fact that the change in this difference correlates directly with the gas flow.

[0020] In another embodiment, the sensor arrangement is based on a differential pressure principle, whereby the gas flow is detected based on the fact that the volume flow is proportional to a pressure difference that is generated via a defined constriction (e.g. orifice, Venturi nozzle).

[0021] In another embodiment, the sensor arrangement is based on an ultrasonic principle, wherein ultrasonic waves are sent against and with the flow direction, the gas flow is detected based on a transit time difference of the ultrasonic waves, which provides information about the flow rate.

[0022] In another embodiment, the sensor arrangement is based on a Coriolis principle (for mass flow), wherein the gas flow is detected based on the fact that a deformation of a pipe caused by flow can be used to directly detect the mass flow.

[0023] It goes without saying that the sensor arrangement can also be based on a combination of the above-mentioned measurement principles.

[0024] For example, a Sensirion SDP type thermal gas / mass flow sensor could be used. Due to its small size, such a sensor can be positioned directly behind the filter and in front of the valves, and can be directly connected to the microprocessor and power supply.

[0025] In principle, the following types of gas flow sensors could also be used, although in current embodiments these would likely provide a measurement of gas flow differences that is too "coarse" for applications as a pipetting aid within the meaning of the invention: A gas flow sensor for direct volume counting, e.g., a counter with a constant measuring chamber volume (such as a drum meter), a counter with a variable measuring chamber volume, or an oval gear counter. Alternatively or additionally, an indirect volume counter could be used, e.g., a magnetic-inductive flow meter.

[0026] For example, the value of the signal transmitted to the pump determines the operating point or pumping capacity. Linking the actuation button's travel to the pump's operating point allows the user to continuously aspirate and dispense liquid between 0% and 100% pumping capacity.

[0027] Simultaneously, the dispensing and aspiration behavior can be determined by the pump. The magnitude of the overpressure or underpressure determines the volumetric flow rate into or out of the pipette and thus the flow rate of the liquid to be aspirated or dispensed. This provides the user with improved tactile feedback when using the pipetting device, as the movement of the actuation button directly affects the volumetric flow rate of the liquid. It is known in the prior art to achieve stepless operation of the pump, for example, by combining a stepped pump with a continuously adjustable valve and optionally with a pneumatic damper.

[0028] However, the use of a continuously variable pump, i.e. a pump with continuously adjustable pumping power, offers the advantage that a liquid with minimal volume flow can be aspirated or dispensed using a pipetting aid according to the invention, whereby the volume flow is not abruptly reduced to zero in contrast to the currently common embodiments.

[0029] In one embodiment, the pipetting aid has a gas flow sensor on the line between the receiving device and the pump, and the gas flow in this line is coupled to the level of the analog signal. The gas flow sensor measures the volumetric or mass flow rate of the gas mixture in the line. This volumetric or mass flow rate depends on the pressure differential generated by the pump. Thus, the gas flow can be adjusted by controlling the pump. The user can determine the pump's operating point, and therefore the volumetric flow rate of the liquid to be aspirated or dispensed, using the movable actuation button. The level or value of the signal generated by the pressure-sensitive sensor determines the volumetric flow rate.

[0030] Alternatively, the gas flow can be measured either by mass flow or volumetric flow. For any necessary conversion of the measured values, the processor can incorporate various measured variables such as pressure, temperature, and optionally humidity, etc. Alternatively, the measured values ​​can be obtained in a pre-converted form from a suitably designed sensor.

[0031] Advantageously, the control unit features a microprocessor and memory containing a program that converts the analog sensor signal into a digital signal. Crucially, no information from the analog signal is lost during this conversion. Converting to a digital signal offers the advantage of easier transmission, processing, and input to other devices, such as a pump. While it's also possible to control the pump with an analog signal, a digital signal has the advantage of being less susceptible to interference and easier to manipulate.

[0032] Preferably, the program is designed to convert the signal such that the transfer function is linear with respect to the pump power. A linear transfer function has the advantage of establishing a directly proportional relationship between the key travel of the actuator button and the volume flow rate delivered by the pump.

[0033] In an alternative embodiment, however, it is conceivable that the program is designed to convert the signal such that the transfer function for the pump output is non-linear, in particular exponential. A non-linear transfer function can generate increased sensitivity of the pump operation to the actuation point of the push button. An exponential transfer function allows for an almost linear relationship between the actuation point of the push button and the mass or volume flow rate delivered by the pump at small actuation points, whereby this relationship changes with increasing actuation point, so that a larger mass or volume flow rate is delivered for a given actuation point movement than with a linear transfer function.Thus, a small change in the stroke of the actuating button results in a significant change in the mass or volume flow rate at a large mass or volume flow rate, and better control can be achieved at small mass or volume flow rates, since larger movements have a smaller impact.

[0034] Preferably, the pipetting aid includes a handle, and the actuation button(s) is / are located on the handle. The placement of the actuation button on the handle allows a user to hold the pipetting aid with only one hand while simultaneously dispensing or aspirating a liquid. Thus, neither the use of the second hand nor changes in hand position while holding the pipetting aid are necessary. The handle is preferably ergonomically shaped so that a user can hold and operate the pipetting aid with one hand.

[0035] In a preferred embodiment, the actuating button is biased into its rest position by a compression spring. To actuate the button, the user must move it against the force of the compression spring. This provides the user with tactile feedback about the button's movement, as the contact pressure increases with increasing movement. Preferably, the pump's operating point is determined by the spring force of the actuating button's compression spring.

[0036] The pump is advantageously a diaphragm pump. The diaphragm pump is suitable for use in the pipetting aid according to the invention due to its high reliability.

[0037] Preferably, the pump for generating the negative or positive pressure is a piezoelectric pump. The use of a piezoelectric pump has the advantage of enabling stepless operation, which is highly beneficial for use in a pipetting aid. Furthermore, a piezoelectric pump is small and lightweight, making it particularly suitable for use in a portable pipetting device. During operation, the piezoelectric pump is quiet, which in turn increases user comfort when working with a pipetting aid that incorporates a piezoelectric pump.

[0038] A piezoelectric pump is a microdiaphragm pump that uses disc-shaped piezoelectric actuators. The mechanical properties of piezoelectricity are used to move liquids or gases. The general structure of a piezoelectric microdiaphragm pump is as follows: One or more disc-shaped piezoelectric actuators are mounted on a flexible diaphragm. This piezoelectric actuator serves as the pump's drive element. The diaphragm is often made of an elastic material that can bend or deform. Optional inlet and outlet valves control the flow of the medium into and out of the pump chamber. Double-acting piezoelectric diaphragm pumps have two pump chambers instead of just one.

[0039] In a further preferred embodiment, the pipetting aid has a second actuation button which generates a second actuation signal depending on the button stroke, wherein the first actuation signal of the first actuation button creates a negative pressure and the second actuation signal of the second actuation button creates a positive pressure in the pipetting device. Pressing the first actuation button, for example, activates the aspiration mode and pressing the second actuation button initiates the dispensing of the liquid.

[0040] The two control buttons can be used to operate one or more valves, which determine the pump's direction of flow. Depending on the valve's position during pump operation, the pressure in the pipetting aid is either increased or decreased. Two 3 / 2-way valves (three ports, two positions) can be used, as well as a 5 / 3-way valve (five ports, three positions). The user can control the pump's operation in both directions by pressing the control buttons.

[0041] The pipetting aid preferably has a third actuation button, which can be used to activate a switch that initiates the dispensing of a predetermined amount of liquid (aliquot) or releases the vacuum in the pipetting aid so that the entire amount of liquid is dispensed. Actuation of the third actuation button can generate a digital signal that releases the vacuum or creates a positive pressure in the pipetting device, wherein the release of the vacuum in the pipetting device is temporary and the vacuum is restored after a predefined time period or after a predefined volume or mass has passed through.

[0042] Alternatively, pressing the third actuation button can generate a digital signal that causes an increase in the vacuum in the pipetting device, whereby the increase in the vacuum in the pipetting device is temporary and the original vacuum is restored after a predefined time period or after a predefined volume or mass has passed through.

[0043] The third actuation button can temporarily release the vacuum, thus dispensing a precisely defined quantity of liquid from the pipette. Either the duration of the vacuum release determines the dispensed volume, or the volume of liquid to be dispensed determines the duration of the vacuum release. To determine the dispensed volume, the gas flow in the line between the receiving device and the pump is measured and regulated. Within a predefined timeframe, the dispensed volume can be adjusted by varying this gas flow. If the quantity of liquid to be dispensed is known, the duration of the vacuum release can be made dependent on this quantity. In this case, after the desired quantity has been dispensed, the vacuum release is released, and the dispensing stops when the vacuum is restored.

[0044] Unlike the first two actuation buttons, the third actuation button is preferably not linked to the key travel. This means that the command to release a vacuum or create a positive pressure is given by simply pressing the third actuation button. This effect can be repeated as often as desired by repeatedly pressing the button, thus achieving, for example, the repetitive dispensing of a constant partial quantity of liquid. The procedure described above can also be used analogously for the intake of a specific quantity of liquid.

[0045] The integration of a gas flow sensor to measure mass or volume flow has the advantage that the amount of liquid to be aspirated or dispensed can be calculated based on the prevailing pressure. This means that the user is no longer responsible for ensuring the correct dispensed volume; this can be left to the pipetting device. The only remaining task for the user is to communicate the desired volume of liquid to the control unit.

[0046] In another embodiment, the pipetting device incorporates a pressure sensor for measuring the ambient pressure. By determining the prevailing differential pressure, it is possible to calculate and optionally display the current amount of liquid in the pipette. The pressure measured by the pressure sensor is used as an auxiliary value to determine the static situation in the pneumatic system. This allows for an even more precise determination of the gas flow. In other words, unlike the sensor arrangement for detecting the gas flow, the pressure sensor signal contributes a more static value, and, for example, a more static (and not dynamic) pressure sensor signal is generated during pipetting dispensing or retrieval (compared to the signal from the sensor arrangement for detecting the gas flow).

[0047] The control system is advantageously linked to an accelerometer. With the help of the accelerometer, for example, the position of the pipette relative to the vertical can be determined, which in turn can be used to calculate the amount of liquid to be drawn in or dispensed.

[0048] As described above, the line is connected to a gas flow sensor, which in turn is connected to the control unit. Preferably, the control unit is also connected to a temperature sensor that measures the temperature in the line between the pump and the receiving device.

[0049] The present invention also relates to a method for operating a pipetting device (designed to hold a pipette), in particular for aspiration or dispensing of a liquid. In this method, a pump of the pipetting device with continuously adjustable pumping capacity is continuously controlled by means of variable pressure on an actuating button and by sensing a gas flow in a line between a receiving device for the pipette and the pump. For example, the pumping capacity is controlled depending on a signal from a sensor connected to the actuating button (e.g., a pressure-sensitive one), wherein the actuating button signal can assume a multitude of values ​​depending on the button pressure.

[0050] For example, the mass or volume flow rate is recorded or measured in the pipeline, and the pump output is regulated accordingly.

[0051] In another embodiment, a pressure in the line (which is output more statically compared to the dynamically measured gas flow in the line) is also measured to control the pump output. For example, a static pressure value is used as an auxiliary measure during the control process.

[0052] Depending on the measured mass or volume flow rate and, for example, the measured pressure, the aspirated or dispensed amount of liquid can be calculated. This has the advantage that the user no longer has to dispense by eye, but can leave this to the pipetting device according to the invention.

[0053] According to an advantageous variant of the method, the deviation of the pipette's longitudinal axis from the vertical is additionally taken into account when calculating the aspirated or dispensed volume of liquid. This has the advantage that the user no longer needs to ensure that the pipette is positioned vertically during dispensing.

[0054] It is conceivable to also measure the temperature in the line. This is advantageous if there are significant differences between the ambient temperature and the temperature in the aspiration line of the pipetting device.

[0055] To achieve high pipetting accuracy, the pipetting device with the gas flow sensor is preferably calibrated beforehand using a calibrated external mass or volume flow sensor.

[0056] Preferably, the external pressure and the internal pressure are taken into account when calculating the amount of fluid aspirated or dispensed.

[0057] The optional features mentioned can be implemented in any combination, provided they are not mutually exclusive. In particular, where preferred ranges are specified, further preferred ranges result from combinations of the minima and maxima mentioned in those ranges.

[0058] The invention is described in more detail below with reference to the figures. They show: Figure 1: a section through a receiving device of a prior art pipetting aid; Figure 2: a perspective view of a pipetting device consisting of a pipetting aid and a first embodiment of a pipette receiving device according to the invention; Figure 3: a perspective view of only the pipetting aid of Fig. 2 , in which the pipette holding device has been removed; Figure 4: a perspective view of only the holding device of Fig. 2in enlarged scale and matching the pipetting aid of the Fig. 3 Figure 5: an exploded view of the recording device of Figure 4 Figure 6: a longitudinal section through the front part of a pipetting aid with a receiving device; Figure 7: a cross-section through the receiving device of Fig. 6 from the front; Figure 8: a perspective view of the receiving device according to the invention with pipette; Figure 9: a perspective view of a partially cut-away receiving device with a slightly modified design of the clamping blocks; Figure 10: a schematic representation of the components of the pipetting device, with the valves shown in the aspiration position; Figure 11: a side view of the pipetting device with one housing half removed; and Figure 12: the device for measuring the contact pressure of the operating buttons on a strain gauge.

[0059] The in Figure 1The holding device 211 of a pipetting aid shown, according to the current state of the art, has already been described in the introductory section. Its main disadvantage is that pipettes held in the pipette holder are not held securely, but can swing back and forth during handling.

[0060] The in the Figures 2 to 8 The pipetting device 11 shown comprises a motor-driven pipetting aid 13 and a first embodiment of a pipette holding device 15 according to the invention. Figure 2 For illustrative purposes, a pipette 16 is shown in the holding device 15. The pipetting aid 13 has a handle 12 and operating buttons 14 with which the aspiration or dispensing of a liquid can be controlled.

[0061] The essential components of the receiving device 15 according to the invention are a pipette holder 17, a filter 19 adjoining it, and a clamping device 21, which provides additional support to a pipette held in the pipette holder 17. These components of the receiving device 15 are housed in a casing 23, which comprises an approximately semicircular cylindrical shell 25 and a circular base 27 arranged thereon. The base 27 has a central circular opening 29 through which the rear end of a pipette, which in the case of pipettes with larger volumes is a circular cylindrical neck tapered in diameter, can be inserted into the pipette holder 17.

[0062] A head section 31, to which the housing 23 can also be attached, serves to hold the pipette holder 17 and simultaneously acts as a connecting element to the pipetting aid 13. The head section 31 has a substantially rectangular frame with two side walls 33a, 33b, a bottom wall 35, and a top wall 37. A short distance from the bottom wall 35 is an intermediate bottom wall 39. The space 41 between the top wall 37 and the intermediate bottom wall 39 provides a precise fit for the pipette holder 17. A circular recess 41 is provided in the intermediate bottom wall 39, the diameter of which can be slightly larger than the insertion opening 43 of the pipette holder 17. Fig. 6The side walls 33a, 33b have rectangular, laterally projecting bulges 45 adjacent to the intermediate floor wall 39. These bulges serve to receive outwardly projecting retaining flanges 47 molded onto the base of the pipette holder 17. This positive-locking connection prevents the pipette holder 17 from slipping when a pipette is clamped in it.

[0063] A novel feature of the described holding device is that a pipette is held not only by the pipette holder 17 alone, but also by an additional clamping device 21, which is arranged between the base 27 of the housing 23 and the bottom wall 35 of the head 31. In the preferred embodiment shown, the clamping device 21 comprises three clamping jaws 49, each of which includes a short, straight central section 51 and two wings 53 projecting from the central section 51 at an angle of approximately 120 degrees. On the rear side of the clamping jaws 53, two spaced-apart, parallel ribs 55 are provided, between which a spring 57 can be placed.

[0064] A circumferential, upwardly projecting rim 59 is formed on the circumference of the base 27 of the housing 23. From this rim, pairs of spaced-apart, approximately quarter-circle walls 61 project radially. These walls interact with the webs 55 to delimit the clamping jaws 49 and the springs 57 arranged between the webs 55. The springs 57 pre-tension the clamping jaws 49 radially so that they touch in the rest position.

[0065] To facilitate the insertion and clamping of pipettes of varying diameters, a sloping surface 63 is provided on the clamping jaws 49, such that a large insertion opening is located at the bottom and a small exit opening at the top, with the insertion opening being approximately 10 mm and the exit opening between 3 and 4 mm. This ensures easy insertion of the pipettes without significant resistance and the clamping of pipettes with a small diameter of up to 4 mm.

[0066] In the assembled state, the bottom wall 35 of the head section 31 rests on the walls 59 and further spacers 65, so that there is a space between the housing bottom 27 and the bottom wall 35 for receiving the clamping device 21.

[0067] For the detachable connection of the head 31 to the pipetting aid 13, a snap-fit ​​or latching connection and a positive-locking connection are provided. To achieve the positive-locking connection, two inverted, L-shaped ribs are formed on the top wall 37, the shorter legs 69 of which are oriented laterally outwards. The legs 69 fit into lateral insertion slots 71 formed on the housing of the pipetting aid 13. These lateral insertion slots 71 are located between a housing top 73 of the pipetting aid and two ribs 75 that project inwards from the inner wall of the housing at a short distance from the housing top 73. The distance between the mutually oriented ribs 75 is only slightly greater than the distance between the two angled ribs 67 of the head 31.

[0068] The locking connection is achieved by two pushbuttons 77, which are arranged on the outside of the side walls 33a, 33b. The pushbuttons 77 are connected to L-shaped latches 79, the outwardly oriented legs 81 of which can engage in undercuts 85 of the pipetting aid provided on the lateral housing walls 83. The pushbuttons 77 are each pre-tensioned outwards by spring means (not shown in the figures). It is conceivable that the plastic part itself could be resilient and that the pushbuttons 77 and the legs 81 could, for example, be arranged on a resilient plastic beam. By pressing the pushbutton, the latches 79 can be moved inwards far enough that the locking connection between the receiving device 15 and the pipetting aid 13 is released and the pipetting device 15 can be removed from the pipetting aid 13.

[0069] From the sectional views of the Figures 6 and 7The internal structure of the receiving device is shown in more detail. It can be seen that a forward-projecting hook 87 is formed on the head part 31, which can form a positive connection with an angled part 89 provided on the inside of the housing 23 in order to attach the housing 23 to the head part 31.

[0070] According to a separate, independent aspect of the invention, a compact design of the receiving device 15 is achieved by arranging the flat filter housing 91 of the filter 19 not perpendicular to a central axis 93 of the receiving device 15, but parallel to it. This is achieved by arranging the pipette receiving channel 95 and the line section 97, which serves to receive a connecting nozzle 99 of the filter 19, at a right angle to each other ( Fig. 6This arrangement has the advantage that the filter 19 is easily accessible and no housing part needs to be unscrewed to replace the filter 19. It goes without saying that the pipe section 97 and the connecting piece 99 are slightly conical and / or have sealing lips to ensure a secure fit of the filter 19 in the pipette holder 17 and a gas-tight connection between the pipette holder 17 and the filter 19. Alternatively or additionally, sealing lips can be provided to achieve a good seal.

[0071] A space 103 can be provided between the intermediate floor wall 39 and the floor wall 35, where a section of the pipette neck 105, several millimeters long, is exposed and optically accessible from the front or from the pipetting aid. A sensor 107 installed in the pipetting aid opposite the space 103 can thus detect the presence of a pipette 16 marked accordingly on the pipette neck ( Figs. 7 and 8 In combination with a suitable marking on the pipette, e.g. barcode or similar, the pipette type (maximum filling volume) can be determined, for example.

[0072] In Figure 6 It can be seen that the second connecting nozzle 109 of the filter housing 91 is inserted into an elastically deformable connecting part 111 of the pipetting aid in the operational state of the pipetting device.

[0073] In Figure 9A slightly modified second embodiment of a clamping device 21 is shown. This differs from the clamping device described above in that the clamping jaws 49 have a trapezoidal shape in plan view. An elongated guide rail 60 is provided on the upper side of each trapezoidal clamping jaw 49, which can interact with a guide groove 62 on the underside of the intermediate floor wall to guide the clamping jaws 49 in a radial direction.

[0074] Fig. 10Figure 11 shows a schematic representation of the components of a pipetting device. In the figure, the pneumatic lines are shown with solid lines and the electrical lines with dashed lines. The pipetting device 11 has a pump 121, which is connected on one side via a line 123 to a multi-way valve 125 and on the other side via a line 127 to a multi-way valve 129. The multi-way valves 125 and 127 are in turn connected to each other and also to two one-way valves 133 and 135 via a line 131. It is conceivable that the two functions are combined in a single component. From the one-way valves, a line 137 leads via the filter 19 to the pipette holder 17. The one-way valve 135 opens automatically when air is drawn in, i.e., aspirated, and the one-way valve 133 opens when liquid is dispensed. Figure 10The figure shows the multi-way valves 125,129 in the aspiration position, i.e., the multi-way valve 125 is open and the multi-way valve 129 is closed, so that air is drawn in via the lines 123,131 and 137.

[0075] Sensors for measuring the physical properties of the air flowing through the pipe are installed in conduit 137. These sensors could be, for example, a temperature sensor 139, a pressure sensor 141, and a mass flow sensor 143.

[0076] A control unit 145 with a storage unit 147 is provided for controlling the multi-way valves 125, 129 and the pump 121. The control unit 145 is connected via control lines 149 to the operating buttons 14a, 14b, and 14c on one side and to the multi-way valves 125, 129, and the pump 121 on the other. The pump motor and the control unit are powered by a rechargeable battery (not shown in the diagram). An interface 151 allows communication with the control unit 145. This interface could be, for example, a keypad, a touchscreen display, or a wireless communication connection.

[0077] As the scheme of Figure 10As can be seen, the mass sensor 143 does not measure the volumetric flow rate directly in line 137, but in a bypass line 153. The volumetric flow rate in the bypass line is only a fraction, typically between 1 and 10 percent, of the volumetric flow rate in line 137. This is what makes it possible to integrate a gas flow sensor into a battery-operated handheld pipette, because currently available gas flow sensors for measuring volumetric flow rates up to several hundred ml / s are simply too large for integration into a handheld pipette.

[0078] The bypass line can be part of the gas flow sensor, especially when a thermal measuring principle, an ultrasonic sensor, or a Coriolis sensor is used. For example, the bypass line is formed by a supply line and a return line with the gas flow sensor in the middle.

[0079] When using a differential pressure-based measuring system, the bypass line can be replaced by two connections to a differential pressure sensor, meaning that no part of the main gas flow passes through the sensor.

[0080] In addition to the sensors already described above, the pipetting device 11 also has a second pressure sensor 155 for measuring the ambient pressure and an accelerometer 157. Knowing the ambient pressure and the pressure in the line 137, the pressure difference can be taken into account when calculating the amount of liquid to be aspirated or dispensed using the general gas law (P·V=n·R·T).

[0081] Figure 11Figure 11 shows the internal workings of the pipetting device 11 in more detail. The operating buttons 14a and 14b are mounted on a circuit board 161 by means of a foot 159. The operating buttons 14a and 14b are movably held in their rest position perpendicular to the circuit board 161 by a spring 163. The spring 163 is supported on a bending tab 165, on which a strain gauge 167 is mounted and firmly connected to the circuit board 161, e.g., via a soldered connection. Figure 12 ). Handle 12 also contains a rechargeable battery 169 to power the electronics.

[0082] The pipetting device works as follows: In Fig. 10 The aspiration position of the pipetting device is shown. In this position, air is drawn in from the environment via line 123, multi-way valve 125 and lines 131 and 137, and released back into the environment via line 127 and multi-way valve 129.

[0083] When both multi-way valves 125, 129 are moved to the other position, the pump 121 draws in ambient air via the multi-way valve 125 and the line 123 and conveys it via the line 127, the multi-way valve 129, the line 131 and the one-way valve 133 and the line 137 into a pipette 17 held in the pipette holder 17 (dispensing).

[0084] The control buttons 14a, 14b, and 14c can be used to perform aspiration (e.g., control button 14a), dispensing (e.g., control button 14b), or the metered delivery of a specific volume of fluid (e.g., control button 14c). Unlike control buttons 14a and 14b, control button 14c is only connected to a simple on / off switch 171. When switch 171 is activated, a volume of fluid previously entered via the interface or stored in memory is dispensed.

[0085] The built-in sensors (mass or volumetric flow rate and pressure sensor, and optionally a temperature sensor) are used to calculate the aspirated liquid volume. With additional knowledge of the liquid's specific gravity, the aspirated or dispensed liquid volume can be precisely calculated and set. The integrated accelerometer also allows for compensation of the pipette's tilt (deviation of the pipette's longitudinal axis from the vertical) and changes in the liquid's weight. To achieve high accuracy, it is advantageous to calibrate the pipetting device with the flow sensor using an external, calibrated flow sensor. For liquids with viscosities and densities different from water, a correction factor can be determined by the user.

[0086] Summary: A pipetting device has a receptacle for a pipette intended for the aspiration and dispensing of a liquid. The pipetting device 11 comprises a receptacle 17 for a pipette, a pump 121 with continuously adjustable pumping capacity, and at least one valve for controlling the pumping direction such that, during operation, the pump 121 generates either positive or negative pressure in the receptacle 17, depending on the position of the valve. Furthermore, the pipetting device 11 comprises at least one actuating button 14a for switching on the pump 121 and controlling the valve.The pipetting device 11 is characterized in that the actuating button 14a in conjunction with a sensor which is connected to a control unit is designed to generate a signal which can assume a variety of values ​​between zero and a certain maximum level, wherein the control unit continuously controls the pumping power of the pump depending on the respective assumed level of the signal. REFERENCE MARK LIST:

[0087] 11 Pipetting device 12 Handle 13 Pipetting aid 14 Operating buttons 15 Pipette holder 16 Pipette 17 Pipette holder 19 Filter 21 Clamping device 23 Housing 25 Cylinder jacket 27 Base 29 Base opening 31 Head 33a, 33b Side walls 35 Base wall 37 Top wall 39 Intermediate base wall 40 Space for pipette holder 41 Recess 43 Pipette holder insertion opening 45 Protrusion in the side walls 33a,33b 47 Retaining flanges 49 Clamping jaws 51 Center section 53 Wings 55 Webs 57 Spring 59 Edge 60 Guide rail 61 Walls 62 Guide groove 63 Inclined surface of clamping jaws 65 Spacers 67 L-shaped webs 69 Legs 71 Insert compartments 73 Housing top 75 Webs 77 Pushbuttons 79 Latches 81 Legs 83 Side housing wall 85 Undercut 87 Hook 89 Angle part 91 Filter housing 93 Center axis 95 Pipette receiving channel 97 Pipe section 99 First connection 101 Longitudinal axis 103 Space between intermediate wall and housing bottom 105 Pipette neck 107 Sensor 109 Second connection 111 Connection part 121 Pump 123, 127, 131, 137 Lines 125, 129 Multi-way valves 133, 135 One-way valves 139 Temperature sensor 141 First pressure sensor 143 Gas flow sensor 145 Control unit 147 Data storage 149 Control lines 151 Interface 153 Bypass line 155 Second pressure sensor 157 Accelerometer 159 Base of operating buttons 161 Circuit board 163 Spring 165 Brace 167 Strain gauge 169 Battery 171 Switch

Claims

1. Pipetting device for receiving a pipette (16), wherein the pipette is intended for aspiration and dispensing of a liquid, comprising: - a receiving device for receiving a pipette, - a pump (121) pneumatically connected to the receiving device (15) via a line, - at least one valve (125) arranged in the line for interrupting the flow of fluid from the receiving device (15) to the pump (121), - a control unit (145) connected to the pump (121), and - at least one actuating button (14a) also connected to the control unit (145) for controlling the pump (121) and the valve (125). characterized by the fact thatthe pipetting device has a sensor arrangement (139, 141, 143, 153) configured for detecting a gas flow in the line, wherein the pipetting device is configured to continuously control a pumping power of the pump by means of an actuation key signal generated by variable key pressure of the actuation key and the detection of the gas flow.

2. Pipetting device according to claim 1, wherein the actuating button (14a) is connected to a pressure-sensitive sensor (167) and the actuating button signal changes with the pressure intensity.

3. Pipetting device according to one of the preceding claims, wherein the actuating button (14a) is movable and the value of the actuating button signal varies depending on its button stroke.

4. Pipetting device according to one of the preceding claims, wherein the actuation button signal is an analog signal and the pumping power of the pump (121) is coupled to the level of the analog signal, in particular wherein the level of the analog signal is greater the greater the movement of the actuation button.

5. Pipetting device according to one of the preceding claims, wherein the actuating button (14a) is biased into the rest position by a compression spring (163), in particular wherein the compression spring (163) is supported on a bending tab (165), in particular wherein the bending tab (165) is connected to a strain gauge in (167).

6. Pipetting device according to one of the preceding claims, wherein the line is connected to a bypass line (153) and the sensor arrangement (139, 141, 143, 153) is configured to provide the detection of the gas flow in the line by detecting a gas flow in the bypass line (153).

7. Pipetting device according to claims 4 and 6, wherein a gas flow in the bypass line is coupled to the level of the analog signal.

8. Pipetting device according to one of the preceding claims, wherein the pipetting device has a gas flow sensor (143) in the line between the receiving device (15) and the pump (121) which is configured to measure the mass or volume flow in the line, wherein the pipetting device is configured to control the pump power depending on the mass or volume flow in this line.

9. Pipetting device according to claim 8 and claim 6 or 7, wherein the gas flow sensor (143) measures the mass or volume flow in the bypass line (153).

10. Pipetting device according to one of the preceding claims, wherein the pump (121) is a diaphragm pump, in particular wherein the pump (121) is a piezoelectric pump.

11. Pipetting device according to one of the preceding claims, wherein the pipetting device has a further actuating button (14c) the actuation of which generates a digital signal, wherein this signal causes a resolution of a negative pressure or a positive pressure in the pipetting device, wherein the pipetting device is configured such that the resolution of the negative pressure is temporary and the negative pressure is regenerated after a predefined time period or after a predefined volume or mass has passed through the line.

12. Method for operating a pipetting device designed to receive a pipette (16), characterized by the fact that A pump (121) of the pipetting device with continuously adjustable pumping power is continuously controlled by means of variable key pressure of an actuating button (14a) and a detection of a gas flow in a line between a receiving device (15) for receiving the pipette and the pump (121).

13. Method according to claim 13, wherein a mass or volume flow is detected in the line and the pump power is controlled depending on this.

14. Method according to claim 14, wherein a pressure in the line is further measured to control the pump output.

15. Method according to claim 13 or 14, wherein an aspirated or dispensed amount of liquid is calculated depending on the detected mass or volume flow rate and in particular depending on the measured pressure, wherein the deviation of the pipette longitudinal axis (93) from the vertical is additionally taken into account in the calculation of the aspirated or dispensed amount of liquid.

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