Pipetting device and method for producing same

Abstract

The invention further relates to a method for producing said pipetting device. The invention relates to a pipetting device, in particular for pipetting a fluid sample by suctioning into a pipetting container using air under a pipetting pressure, having the following: —a valve assembly with at least one valve device for adjusting a pipetting pressure, said valve device having a valve chamber; —at least one pump device which is connected to the valve chamber in order to generate a chamber pressure in the valve chamber; —a pipetting channel which is connected to the pipetting container, and—a bypass channel which is open towards the surroundings, wherein—the pipetting channel and the bypass channel are each connected to the valve chamber; and—the at least one valve device has a closure element with a closure surface which is designed such that the chamber pressure is distributed to the pipetting channel and the bypass channel in a metered manner by the valve device in order to generate the desired pipetting pressure in the pipetting channel. The invention further relates to a method for producing said pipetting device.

Claims

1. A pipetting apparatus (7), in particular for pipetting a fluid sample (9a) by suctioning into a pipetting container (9) using air (9b) under a pipetting pressure, comprising: a valve assembly having at least one valve device (101) for adjusting a pipetting pressure, wherein the valve device comprises a valve chamber (106); at least one pump device (7) connected to the valve chamber in order to generate a chamber pressure in said valve chamber; a pipetting channel (103) connectable to the pipetting container and a bypass channel (104) which is open to the surroundings; wherein the valve chamber has a first chamber opening (113) connected to the pipetting channel and a second chamber opening (114) connected to the bypass channel, wherein the valve device comprises a closure element (110; 110a; 110b; 110c; 110d) at least partially disposed within the valve chamber which can be moved relative to the valve chamber by a user-controlled movement (B) and has at least one closure surface (120; 120a; 120b; 120c; 120d) which slides along said chamber openings parallel to the first and parallel to the second chamber opening during the movement and closes them as a function of the position of the closure surface, and wherein the at least one closure surface is formed such that in order to generate the desired pipetting pressure in the pipetting channel, the chamber pressure is distributed to the pipetting channel and the bypass channel as a function of the position of the at least one closure surface at the first and second chamber opening.

2. The pipetting apparatus according to claim 1, wherein the closure element comprises at least one recess (121; 122; 121a; 122a; 121b; 122b; 121c; 122c; 121d; 122d) which extends from the closure surface into the depth of the closure element and forms at least one closure surface opening in the closure surface, wherein said at least one closure surface opening has a length measured parallel to the direction of the movement (B) and a width measured perpendicular thereto, wherein the width of the at least one closure surface opening and/or the depth of the at least one recess varies at least sectionally in the direction of the movement, and in particular the closure surface with the at least one closure surface opening slides along the first and/or second chamber opening such that the closure cross section of the first and/or second chamber opening varies during the movement.

3. The pipetting apparatus according to claim 1, wherein the closure element comprises a first recess (121; 121a; 121b; 121c; 121d) which extends from the closure surface into the depth of the closure element and forms a first closure surface opening in the closure surface, and wherein the closure element comprises a second recess (122; 122a; 122b; 122c; 122d) which extends from the closure surface into the depth of the closure element and forms a second closure surface opening in the closure surface, wherein the first closure surface opening lies against the first chamber opening and the second closure surface opening lies against the second chamber opening during the movement.

4. The pipetting apparatus according to claim 3, wherein the width of the first closure surface opening and/or the depth of the first recess increases at least sectionally in the direction of movement and wherein the width of the second closure surface opening and/or the depth of the second recess decreases at least sectionally in the direction of movement.

5. The pipetting apparatus according to claim 1, wherein the first chamber opening and the at least one closure surface define a first connecting channel with a variable first flow resistance R1, wherein said first connecting channel connects the pipetting channel to the valve chamber, and wherein the second chamber opening and the at least one closure surface define a second connecting channel with a variable second flow resistance R2, wherein said second connecting channel connects the bypass channel to the valve chamber, wherein the distribution of the chamber pressure on the pipetting channel and the bypass channel changes the R2/R1 ratio, wherein the ratio in particular increases during the movement.

6. The pipetting apparatus according to claim 1, wherein the closure element comprises at least one first closure surface and one second closure surface which are not parallel and in particular oriented at an angle of 60°<=α<=120° to each other.

7. The pipetting apparatus according to claim 6, wherein the first closure surface is positioned opposite the first chamber opening and slides along same and the second closure surface is positioned opposite the second chamber opening and slides along same during the movement.

8. The pipetting apparatus according to claim 1, wherein the first and/or second chamber opening comprises a sealing section which the at least one closure surface contacts, particularly to seal the first and/or second chamber opening in substantially completely gas-tight manner in at least one position of the closure element.

9. The pipetting apparatus according to claim 1, wherein the valve chamber or the closure element comprises at least one sealing section in order to seal the valve chamber in substantially completely gas-tight manner in at least one position of the closure element and/or during the movement.

10. The pipetting apparatus according to claim 1, comprising a first valve device having a first valve chamber and a second valve device having a second valve chamber, wherein the pump device is connected to the first valve chamber in order to generate a first chamber pressure in said first valve chamber and connected to the second valve chamber in order to generate a second chamber pressure in said second valve chamber, wherein the first valve chamber and the second valve chamber are in each case connected to the pipetting channel and the bypass channel, wherein the first valve device is designed such that a suitable pressure is set in the pipetting channel for suctioning a fluid sample into a pipetting container hermetically connected to the pipetting channel, and wherein the second valve device is designed such that a suitable pressure is set in the pipetting channel for dispensing a fluid sample from a pipetting container hermetically connected to the pipetting channel.

11. A method for producing the pipetting apparatus according claim 1, comprising the steps: producing the at least one valve device of the valve assembly at least partly from a first material; producing at least one closure element; producing the at least one pipetting channel, and in particular also the at least one bypass channel, at least partly from a second material.

12. The pipetting apparatus according to claim 2, wherein the closure element comprises a first recess (121; 121a; 121b; 121c; 121d) which extends from the closure surface into the depth of the closure element and forms a first closure surface opening in the closure surface, and wherein the closure element comprises a second recess (122; 122a; 122b; 122c; 122d) which extends from the closure surface into the depth of the closure element and forms a second closure surface opening in the closure surface, wherein the first closure surface opening lies against the first chamber opening and the second closure surface opening lies against the second chamber opening during the movement.

Description

(1) Further preferential embodiments and features of the inventive pipetting apparatus and the inventive method for its production will be yielded by the following description of the example embodiments in conjunction with the figures and their description. Identical components of the example embodiments are substantially identified by the same reference numerals unless stated otherwise or otherwise clear from the context. Shown are:

(2) FIG. 1 shows a first example embodiment of the pipetting apparatus according to the invention in a schematic side view.

(3) FIG. 2a shows a cross-sectional view through a valve device of the pipetting apparatus in FIG. 1 according to a first preferred embodiment of the invention in a first state.

(4) FIG. 2b shows the valve device of FIG. 2a in a second state.

(5) FIG. 2c shows the valve device of FIG. 2a in a third state.

(6) FIG. 3a shows an isometric oblique view of an insertable closure element for the valve device of an inventive pipetting apparatus according to a first example embodiment.

(7) FIG. 3b shows an isometric oblique view of an insertable closure element for the valve device of an inventive pipetting apparatus according to a second example embodiment.

(8) FIG. 3c shows an isometric oblique view of an insertable closure element for the valve device of an inventive pipetting apparatus according to a third example embodiment.

(9) FIG. 3d shows an isometric oblique view of an insertable closure element for the valve device of an inventive pipetting apparatus according to a fourth example embodiment.

(10) FIG. 3e shows an isometric oblique view of an insertable closure element for the valve device of an inventive pipetting apparatus according to a fifth example embodiment.

(11) FIG. 4 shows an isometric oblique view of the valve chamber section with pipetting channel and first chamber opening used in the FIG. 3a valve device of the inventive pipetting apparatus.

(12) FIG. 1 shows one example embodiment of an inventive pipetting apparatus 1. This pipetting apparatus 1 serves as an electrically operated manual pipettor for use with volumetric pipettes or graduated pipettes 9 made of glass or plastic as available from the laboratory supplies trade in different sizes with filling volumes ranging between 0.1 mL (milliliter) and 100 mL.

(13) In describing the invention, the terms “above” and “below” are in particular used. These refer to a spatial arrangement of the pipetting apparatus in which a pipetting container extending along a longitudinal axis and connected to the pipetting apparatus, is disposed parallel to the direction of gravity, i.e. vertically. The “downward” directional indication designates the gravitational direction, the “upward” indication designates the opposite direction.

(14) The pipetting apparatus 1 is an air-cushion pipetting apparatus which in particular serves in pipetting a fluid sample by suctioning it into a pipetting container by means of air under a first pipetting pressure and/or serves in dispensing or pressing a fluid sample out of a pipetting container by means of air under a second pipetting pressure. The air-cushion pipetting apparatus uses air as a working medium in order to effect the transport of the fluid sample into and out of the pipetting container. This will be explained further in the following:

(15) In FIG. 1, the fluid sample 9a is shown as the hatched area in the pipetting container 9. Air which is expanded relative to the ambient pressure, thus under a negative pressure, is located above the hatched area in area 9b of the pipetting container. The negative pressure is the pipetting pressure applied via the pipetting channel to suction the sample, which in FIG. 1 holds the sample 9a in the container at a constant height against the force of gravity. The first pipetting pressure for suctioning the sample is in particular selected such that it is at least lower than the ambient pressure to which the sample to be pipetted is exposed. The first pipetting pressure for suctioning the sample is in particular selected such that it applies the necessary counterforce to raise or maintain the liquid column 9a in the pipetting container 9, said counterforce being in particular substantially at least as great as the weight of the liquid column 9a. The second pipetting pressure for dispensing the fluid sample 9a from the pipetting container 9 must be at least as low as the first pipetting pressure, in particular at least low enough for the liquid column to overcome the counterforce effected by the pipetting pressure (negative pressure) and be dispensed gravitationally. To press the fluid sample out of the pipetting container, the second pipetting pressure is in particular at least greater than the ambient pressure.

(16) The pipetting apparatus 1 comprises a housing 2 as a base body 2 which has a boom section 4 with a connecting section 5 of the pipetting apparatus provided on its lower side end at which the pipetting container 9 detachably and hermetically connects to the connecting section 5. The connecting section is designed here as a replaceable, screwable receiving cone 5. It incorporates a clamping section (not visible) for frictionally holding the pipetting container 9 insertable into the clamping section 9 and a membrane filter (not visible) which is inserted into the pipetting channel between the boom section 4 and the pipetting container 9. The membrane filter prevents the fluid sample to be pipetted from penetrating into the pipetting apparatus or its valve device respectively. This thus ensures the continued functioning of the pipetting apparatus.

(17) The base body 2 further comprises a pistol-like grip section 3. A battery or respectively accumulator unit 6 is arranged in a battery compartment open or openable to the bottom in the interior of said grip section 3. The accumulator unit 6 can comprise e.g. a nickel metal hydride or a lithium polymer or a lithium-ion/polymer accumulator able to provide e.g. an operating voltage of 9V. The accumulator unit 6 can be dislodged downward out of the base body 2 in the manner of a pistol magazine and is preferably held to the base body by a (not shown) latching device. A pump device 7 electrically operated by the operating voltage of the accumulator unit and comprising an electrically operated diaphragm pump of adjustable pumping capacity is additionally accommodated in the interior of the grip section 3. An electrical control device 8 inside the housing 2 comprises electrical circuits, in particular programmable electrical circuits. The control device 8 is designed to control at least one function of the electrically operated pipetting apparatus 1.

(18) Further arranged in the interior of the grip section 3 is a valve assembly with two valve devices which can in particular be designed as per FIGS. 2a to 2c and with which particularly a closure element can be adapted as is shown in one of FIGS. 3a to 3e.

(19) The pipetting apparatus 1 comprises two actuating elements 11, 12 for manually actuating the two valve devices of the valve assembly. The actuating elements are designed as pushbuttons 115 spring-mounted by means of spiral springs 131, their spiral springs 131 tensioned when the user's finger moves the pushbutton out of its initial position into the pressed-in position. The pushbuttons 11, 12 can be moved independently of each other. The two actuating elements 11, 12 are arranged parallel one above the other and horizontally movable and undetachable from the base body 2. Each actuating element 115 in the valve device 101 according to the first preferential embodiment of the invention is preferably rigidly fixed at least in one direction along the A axis (see FIG. 2a) to a closure element 110 of the valve assembly valve device 101, in particular by means of injection molding as an integrally produced component with the closure element 110.

(20) As shown in FIGS. 2a to 2c, the user directs the closure element from the first position, shown in FIG. 2a, into the third position, shown in FIG. 2b, and from there optionally into the second position, shown in FIG. 2c, by way of movement B. If the user exerts a lower force than that applied by the compressed spiral spring 131 between the valve support element 111 and the closure element 110, the closure element is then reset by the spring action.

(21) In the first position, shown in FIG. 2a, the pipetting channel 103 and the first chamber opening 113 of the valve chamber 106 are completely closed by the planar closure surface 120 sealingly contacting the edge of the first chamber opening or the sealing section 113′ realized as a silicone O-ring 113′ preferably provided there respectively so as to prevent gas from passing through the first chamber opening 113, in particular in any typical operating state of the pipetting apparatus. In the context of the present description of the invention, the sealing section shown in FIG. 4 can generally be realized not only as an elastic O-ring but, for example, also be completely configured as an elastomer section of the pipetting channel; in particular, the pipetting channel can be partly or completely made of elastomer. The bypass channel 104 is furthermore open in the first position of the closure element, namely not closed off by the closure surface 120 since the second chamber opening 114 here is situated opposite the second recess 122 of the closure element. The second recess 122 keeps the flow path here maximally opened via the second chamber opening 114 so that a chamber negative pressure or chamber positive pressure, relative to the ambient pressure; i.e. here the atmospheric pressure, effects flow through the bypass channel 104 if the pump device is active and acts on a flow through the pumping channel. However, the pump device is preferably inactive in the first position, in particular by the pump device not being activated until a turn of the actuating knob 115 has been mechanically activated. In the first state of the valve assembly, in particular a liquid column 9a can be held at a constant height by a suitable pipetting pressure (negative pressure) in the pipetting channel.

(22) In the second position, shown in FIG. 2c, the bypass channel 104 and the second chamber opening 114 of the valve chamber 106 are completely closed by the planar closure surface 120 sealingly contacting the edge of the second chamber opening or the sealing section 113′ realized as a silicone O-ring 113′ preferably provided there respectively so as to prevent gas from passing through the second chamber opening 114, in particular in any typical operating state of the pipetting apparatus. The pipetting channel 103 is furthermore open in the second position of the closure element, namely not closed off by the closure surface 120, since the first chamber opening 113 here is situated opposite the first recess 122 of the closure element. The first recess 121 keeps the flow path through the first chamber opening 113 maximally open here so that the chamber negative pressure or chamber positive pressure, related approximately roughly to the ambient pressure (more precisely: relative to the pressure applied with inactive pump and motionless liquid column 9a in area 9b and in the pipetting line which deviates from the ambient pressure due to the gravitational and suction effect of the liquid sample 9a in the pipette 9), effects a maximum air flow through the pipetting channel 103.

(23) In a third position, shown in FIG. 2b, in which the closure element is arranged between the first and second position, the first chamber opening 113 and the second chamber opening 114 are in each case partly open. A first flow resistance thereby ensues through the first connecting channel which is dictated by the flow sections situated between the valve chamber 106 and the pipetting channel 103. Among these flow sections is in particular the section of the first closure surface opening of the first recess 121 adjacent the first chamber opening in this third position which opens to the closure surface 120. A cross section of the first recess 121 changing along the direction of movement B is realized here which can be induced by a recess and/or closure surface opening width changing along direction B or by a depth changing along direction B, see the embodiments of possible closure elements and their recesses in FIGS. 3a to 3e. Due to the changing cross section of the first recess 121 along direction B, a first flow resistance dependent on the position of the closure element is realized.

(24) Similarly, the second connecting channel yields a second flow resistance which is dictated by the flow sections situated between the valve chamber 106 and the bypass channel 104. Among these flow sections is in particular the section of the closure surface opening of the second recess 122 adjacent the second chamber opening 114 in this third position which opens to closure surface 120. Due to the R2/R1 relationship of the second flow resistance R2 to the first flow resistance, the chamber pressure applied in the valve chamber can be distributed or metered respectively to the pipetting channel and the bypass channel so that the user-desired pressure which results in suctioning or expelling the fluid sample 9a from the pipette 9 can be generated in the pipetting channel.

(25) Preferably, the pipetting apparatus comprises a blocking device which automatically blocks, in particular locks, one actuating element 11 when the other actuating element 12 is actuated and vice versa. The blocking device can comprise a locking bar element which is mechanically displaced by an actuating element being actuated so as to block the mobility of the other actuating element in a blocked state. The blocking device can however also be designed to set the blocking state electrically.

(26) The first actuating element 11 serves in the suctioning of the fluid sample into the pipetting container. The second actuating element 12 serves in the dispensing/pressing out of the fluid sample from the pipetting container.

(27) The valve assembly of the pipetting apparatus 1 is constructed of different components in the example embodiment which are in particular joined together. These components in particular comprise a support component (not shown), in particular two closure support elements, two closure elements 110, 110′ and sealing rings, in particular sealing rings 113′. A sealing section, in particular a sealing ring, can in particular be provided in each case at the outer end 132 of the valve chamber 106, or the closure support element 111 respectively, as shown in FIG. 2a. The closure support element 111 can be of a shape with its interior adapted to the shape of the closure element 110 and enables the particularly translational movement B of the closure element 110 within the closure support element 111. To that end, the valve chamber 106 is designed as a receiving section of the closure element 110.

(28) Each receiving section is outwardly open on one side in order to enable the inserting of a first closure element 110, respectively second closure element 110. Each closure element preferably exhibits a small clearance fit relative to its receiving section so that a closure element can in each case be non-positively fixed in the receiving section by the compressing of at least one sealing ring, e.g. at position 132 (FIG. 2a). The sealing rings are preferably of a sealing design so as to produce an airtight and a (negative) pressure-tight seal under the intended use of the pipetting apparatus.

(29) Producing the valve assembly is particularly simple and economical, and thereby efficient, because the cited components can be easily assembled simply by fitting them together, in particular without the use of special tools and/or complicated securing steps when assembling.

(30) The further the closure element 110 is moved into the first position, the larger the volume of air drawn through the bypass channel 104. The volume of air suctioned through the pipetting channel is thereby correspondingly smaller. As a consequence, the lifting speed (volume per time) of the fluid sample into the pipetting container connected to the pipetting channel and the maximum liquid column in the pipetting container is low due to the gravitational force acting on the liquid column. Correspondingly holding true is that the further the closure element 110 is moved into the second position, the smaller of a percentage of air is drawn through the bypass channel 104. The volume of air suctioned through the pipetting channel is thereby correspondingly larger. If the closure element 110 is maximally moved into the closure support element 111 (second position), substantially no further air is drawn via the bypass line 104. The volume of air suctioned out of the pipetting channel 103 thereby achieves a maximum value. In consequence, the lifting speed and the liquid column are in each case at their maximum in the pipetting container. Additionally to controlling the lifting speed via the bypass channel 104, the change in cross section, in particular the conical form to at least one recess (121, 122) of the closure element 110, effects a regulating of the air speed along the airflow path from the inlet into the interior space of the closure support element 111 to the pipetting channel 103. This functionality of the valve assembly will in particular be described below. The lifting speed of the liquid column into the pipetting container can thereby be even more finely regulated.

(31) Should the user, starting from the second state of the valve device 101 in FIG. 2b, convey the closure element 110 from the third position back into the first position in order to stop the suction process, it is preferably provided for the pumping capacity to be regulated in a predetermined manner by the electrical control device such that the pumping capacity is set as a function of the first flow resistance in the first connecting channel so the pipetting pressure remains constant until the closure element again reaches the first position. The liquid column suctioned by the user into the pipetting container thereby remains at a constant volume. When the closure element is moving from the third position into the first position, it is particularly possible for the pumping capacity prevailing in the third position to be kept at least constant until the first position is reached.

(32) The pipetting pressure in the pipetting channel 103 is in each case set by one valve device whereas the other valve device is not substantially affected as particularly the first connecting channel of the other valve device is closed. The second connecting channel or the second chamber is preferably at least partially opened particularly in the third position lying between the position of the closure element in the first and/or second position, and is in particular in a third position which is closer to the first position than the second position, preferably open to at least half of the maximum opening or maximum opening volume. This respective bypass connection of the valve chamber of the valve device to the surroundings in particular achieves the pressure fluctuations in the valve chamber, which can be caused by the pump device, not being transmitted in full to the pipetting channel and thus to the liquid column but rather given off proportionately to the surroundings by the bypass and thus efficiently attenuated, in particular at minor deflections of the valve piston from the first position and particularly at low pumping capacities and/or pump frequencies. At full pumping capacity, even pipetting containers of low dosing volume can be filled very precisely. So doing enables more precise and easy pipetting.

(33) A further adjusting of the pipetting behavior occurs with the pipetting apparatus 1 in that the pumping capacity is infinitely variable. To that end, the base body 2 comprises at least one Hall sensor as a position sensor (not shown), by means of which the position of the closure element is detected relative to the base body or relative to the closure support element 111 respectively. The electrical control device 8 is designed to change the pumping capacity, in particular increase the pumping capacity, as a function of the measured position and/or measured speed of the valve piston 110 along the A axis when the user presses the closure element farther inside the closure support element 111 by gradually pressing the actuating element. Use of the pipetting apparatus is thereby made more efficient, in particular easier, and the adjusting of the pumping capacity more flexible. In particular, the pump can be immediately activated by means of the position sensor or another e.g. mechanical switch. The mechanical switch can, for example, be automatically triggered by a plate on the actuating element when the user pushes the actuating knob out of the starting position, preferably when the user moves the valve piston out of the first position. This applies at least to the actuating element for suctioning in the sample. Preferably provided for the actuating element for dispensing the sample is for the pump to only become active when the closure element 110 reaches a specific third position; i.e. depression depth, since prior to reaching the third position, dispensing is gravity-driven and does not require any positive pressure. Sample dispensing controlled by opening the second connecting channel is efficient and convenient, and the pumping activity can additionally accelerate the dispensing to the desired extent.

(34) A further particular advantage of the inventive pipetting apparatus according to the first preferential embodiment with the valve assembly is as follows: The pipetting apparatus is configured such that substantially only that volume of air is exchanged with the surroundings through the bypass line 104 which corresponds to the volume of air needed to set the desired pipetting pressure in the pipetting channel, whereby an exchange of air substantially occurs preferably only when setting the pipetting pressure and preferably does not substantially occur when the desired pipetting pressure is reached. This exchanged volume of air represents in particular a net flow between the flow regions of the valve assembly and the surroundings, thus either the net volume supply of air from the surroundings or the net volume discharge of air to the surroundings. Thus, less—potentially harmful, e.g. most—external air reaches the channel areas of the valve assembly and, vice versa, less air from the valve assembly is emitted to the surroundings, which makes for a more pleasant user experience.

(35) This is attained in the example embodiment particularly by the pipetting apparatus having exactly one pump device with, for example, exactly one diaphragm pump, and at least one first—or exactly one first—pump channel 105 for the suctioned air, connected on the intake side to the pump device, and at least one second—or exactly one second—pump channel for the emitted air, connected on the discharge side to the pump device, wherein the first pump channel is connected to the first valve chamber of the first valve device and the second pump channel is connected to the second valve chamber of the second valve device so that both the intake pressure in the first valve chamber as well as the discharge pressure in the second valve chamber can be produced by means of the one pump device.

(36) FIG. 3a shows the closure element 110 insertable into an inventive pipetting apparatus 1 according to a first example embodiment. The closure element comprises a first closure surface 120 which is planar and arranged parallel to direction of movement B. When viewed in cross section perpendicular to direction of movement B, the closure element is additionally triangular, here corresponding to an equilateral triangle, the sides being at an angle of cx=60° to each other. Other cross-sectional shapes with other numbers of sides, in particular planar sides, are possible and preferential. The area of the closure element with closure surfaces 120 does not serve as a piston element sealing the interior of the closure support element. It is only provided for the respective closure surface 120, 120′ to be able to slide parallel along the first and second chamber opening 113, 114 in order to fully close them in position-dependent manner or partially close them in gas-tight manner.

(37) The form to the first closure surface differs from the form to the second closure surface. The user can take the closure element out of the closure support element 111, rotate it, and reinsert it such that a different closure surface is facing the first and second chamber opening. A different pipetting behavior of the pipetting apparatus is thereby set, in particular the pipetting speed impacted. The first recess 121 of the first closure surface 120 preferably differs in its width and/or depth from the first recess 121′ of the second closure surface 120′. The second recess 122 of the first closure surface 120 preferably differs in its width and/or depth from the second recess 122′ of the second closure surface 120′.

(38) It is in principle also possible and preferential for the closure element to only comprise one single closure surface in order to realize only one pipetting behavior of the pipetting apparatus. The closure element can then also be non-detachably connected to the closure support element 111.

(39) FIG. 3b shows the closure element 110a insertable into an inventive pipetting apparatus according to a second example embodiment. The closure element is realized similar to closure element 110 but comprises recesses 121a, 122a, 121a′, 122a′ of a substantially constant width so as to result in a rectangular closure surface opening. The changing flow resistance along direction B is in each case substantially attained here by a changing recess depth along direction B.

(40) FIG. 3c shows the closure element 110b insertable into the inventive pipetting apparatus according to a third example embodiment. The closure element is realized similar to closure element 110; i.e. comprising recesses 121a, 122a, 121a′, 122a′ of a substantially constant width so as to result in a rectangular closure surface opening. Here as well, the changing flow resistance along direction B is in each case substantially attained by a changing recess depth along direction B. The recesses here are distributed in pairs one behind the other in direction B about a cylindrical section of the closure element 110b or its only cylindrical closure surface 120b respectively. The user can orient a pair of recesses to the first and second chamber opening by rotating the closure element 110b, whereby the rotational position of the closure element is preferably secured at said orientation by a locking device (not shown).

(41) FIG. 3d shows the closure element 110c insertable into the inventive pipetting apparatus with further adaptation of the chamber opening arrangement according to a fourth example embodiment. The closure element exhibits the cylindrical section with cylindrical closure surface 120c. A first recess 121c tapering in direction B serves to open the pipetting channel, a second recess 122c (not visible) widening in direction B opposite from recess 121c serves to simultaneous close the bypass channel upon movement in direction B. The first and second chamber opening are thereby oppositely arranged on the valve chamber (not shown) corresponding to the position of recesses 121c and 122c. A further pair of recesses 121c′ and 122c′ (not visible) can be adjusted by the user rotating the closure element 110c.

(42) FIG. 3e shows the closure element 110d insertable into the inventive pipetting apparatus with further adaptation of the chamber opening arrangement according to a fifth example embodiment, only differing from closure element 110c by the changing maximum depth of one, multiple or all of the recesses along direction B.

(43) Different closure elements, e.g. closure element 110c and closure element 110d, can preferably be used with the same closure support element.