EP0547503A1 - Pipetting device - Google Patents

Abstract

Pipetting device having a housing (1) and a receptacle (10) formed therein, a pipette tip (3) which has a tubular tip section (3') with a tip orifice (4) for the passage of fluid from outside to inside and vice versa, and a deformation section (8) combined therewith into a unit, the pipette tip (3) with the outwards-projected tip section (3') being inserted in the receptacle (10) and being detachably linked to the housing (1), an actuation device (29) and a setting device (11, 15, 16, 21) linked thereto which bears on the outside of the deformation section (8) in order to compress or expand the latter and a working volume, which is arranged therein and is open towards the tip orifice (4), in accordance with an actuation of the actuation device (29), the internal width of the undeformed deformation section (8) exceeding that of the tip orifice (4), and the setting device (11, 15, 16, 21) deforming the deformation section (8) essentially in a transverse direction over the entire deformation range of the working volume. <IMAGE>

Description

The invention relates to a pipetting device according to the preamble of claim 1.

A pipette of the aforementioned type is known from DE-PS 25 49 477. The closed working volume is formed in a cylinder and adjustable by moving an inserted piston. A linkage acts as an adjustment device, which can be actuated by means of an engaging button. The working volume communicates with the cavity of an attachable pipette tip, so that liquid can be pressed out or drawn in through a lower tip opening by pressing a button.

However, this piston stroke pipette has the disadvantage that contaminated vapors or aerosols released from the sample liquid can get into the upper cylinder space and can be released again in an uncontrolled manner during the subsequent dispensing steps with newly taken in sample material. As a result, contamination of subsequent samples is possible even when the pipette tip is replaced.

To overcome this disadvantage, it has already been proposed to arrange a replaceable filter in the connection area between the pipette tip and the pipetting device. However, this solution uses an additional component with the filter and is still imperfect in terms of shielding the working volume. In particular, the correct replacement time of the filter can be difficult to determine when its maximum absorption capacity is reached. Absolute contamination protection from the upper dosing range is impossible.

Another proposal for a pipetting device protected from contamination is known from EP-A-00 77 180. Accordingly, the pipette tip is sealed by an annular seal on the pipetting device and has a capillary with an insertable piston rod.

A piston is releasably attached to the piston rod with a sealing element, the total length of this sealing element having to be at least twice the cylinder cross section. Before each sampling, a new pipette tip including the piston rod and piston must be connected. Each time the dosing elements are replaced, several disposable parts have to be handled. The outer tip contour and the control unit of the piston must be carefully adapted.

A blood sampling device is known from US Pat. No. 4,210,026. A piece of hose that is closed at one end can be inserted into this between a rigid and a pivotable element. A roller wheel can be moved along the swivel element in order to progressively compress the tube piece. When the wheel is moved back, the piece of tubing can expand again, drawing in a blood sample. In this device, the piece of hose is held securely only when it is compressed over its entire length by the pivotable element. Otherwise it can oscillate between the swiveling and the fixed element, which makes sample collection difficult. If the free space between the two elements is pivoted open relatively far, the piece of hose can fall out. It is difficult to determine from the outside whether it is held in the device. Finally, the sucked-in sample volume is influenced by a certain variability in the arrangement of the tube piece in the device. An exact dosage is therefore not possible with the blood sample collection device.

Proceeding from this, the object of the invention is to improve a pipetting device in such a way that, with increased freedom from contamination, handling is facilitated and improved meterability is achieved.

The solution to this problem is specified in claim 1.

In the case of a pipetting device according to the invention, the variable working volume is not predetermined by a cylinder with an inserted piston, as is the case with a piston-stroke pipette. Instead, it is provided in a deformation section of the pipette tip and can be changed by deforming it using an actuating device. Compressing the working volume thus causes the contents of the pipette tip to be pushed out through the tip opening and expanding the deformation section results in a fluid being sucked in through the tip opening. This only allows the pipette tip to compress or expand the working volume is open towards the tip opening so that only there liquid, vapors or aerosols can escape. After use, the pipette tip, including the deformation section, is disposed of, so that if the contaminated substance does not come into contact with the pipetting device, it cannot be contaminated.

The inside width of the undeformed deformation section exceeds the inside width of the tip opening. In addition, the deformation section is deformed essentially in the transverse direction by the actuating device over the entire deformation region of the working volume. As a result, the deformation section has favorable elastic deformation properties and a deformation favoring the insertion, fixing and metering of the pipette tip is achieved. If the actuating device is not actuated for deformation in the transverse direction, the pipette tip can be inserted with its deformation section in the longitudinal direction into the effective range of the actuating device. By actuating the actuating device, the deformation section can then be deformed in the transverse direction essentially over its entire length, as a result of which the pipette tip is securely fixed to the pipetting device. The pipette tip is relatively rigid in the area of the tip section, so that its alignment to the pipetting device is practically not affected by deformation of the deformation section. The tip opening of smaller clear width can thus be safely brought specifically to a sample to be recorded, even if this is only a punctual occurrence. By pre-deforming the deformation section, in addition to fixing the pipette tip, compensation for misalignments between the deformation section and the actuating device is achieved. The deformation for taking up samples is linked to the pre-deformation. Then a very precise dosing of samples is possible, which can have very different volumes due to the large receiving cross section of the pipette tip.

The deformation section is preferably bubble-like, so that the pipette tip is hermetically sealed everywhere outside the tip opening. In any case, it can have a cylindrical shape, which in particular facilitates insertion of the pipette tip into a pipetting device with a slim, rod-shaped housing. A bellows design with deformability in the transverse direction can also be considered. A shape can be generalized with at least any preferred deformation direction be used.

The pipette tip can have a conical tip section which can accommodate larger amounts of sample in its enlarged cavity. The drawing in of samples into the deformation section and the associated bubbling effects can be avoided. An annular flange between the deformation section and the tip section can facilitate the handling of the pipette tip and its reproducible positioning as well as final disposal via a ring-shaped ejection device. The receptacle preferably has an opening for the axial insertion of the deformation section and an inner contour corresponding to the outer contour of the inserted deformation section.

The actuating device preferably has a metering cylinder with a metering piston guided therein for deforming the deformation section, the metering piston being displaceable by means of a metering element of the actuating device. For simple power transmission, it is sufficient if the actuating device is coupled to the metering piston via a linkage. The linkage can contain a stroke limiter, which has a stop flange fixed to the linkage and at a distance from one another on the housing side has fixed end stops on both sides of the stop flange. The end stops limit the movement of the rod-fixed piston and thus the pipettable sample volume via the stop flange. Furthermore, for the purpose of adjusting the pipetting volume, the distance between the end stops can be changed via an actuating gear.

After connecting the pipette tip to the device, there may be misalignments between the deformation section and the actuating device due to tolerances. The actuating and actuating devices therefore preferably have pre-deformation devices for pre-deforming the deformation section. By pre-deforming the deformation section it is achieved that tolerances in the further deformation of the same no longer play a role in sample dosing. For this purpose, the pre-deformation devices can have a pre-deformation piston for pre-deforming the deformation section. Like the metering piston, the pre-deformation piston can act on the deformation section.

In a preferred, very space-saving design, the preforming piston and metering piston are arranged coaxially in a common cylinder. Preforming pistons and metering pistons can, however, also be arranged side by side in parallel in a preforming cylinder and a Be dosing cylinder.

Dosing pistons and / or pre-deformation pistons can act directly on the deformation section, for example. For a uniform attack of the deformation force, however, it is preferred that the pistons act on the deformation section via a displacement fluid. The displacement fluid is preferably an incompressible medium such as brake or other hydraulic fluid.

In principle, the displacement fluid can act directly on the deformation section, care having to be taken to ensure a suitable sealing of the pipette tip in the pipetting device. In a preferred embodiment, however, the adjusting device has a displacement device made of flexible material with a receptacle for the deformation section, which has at least one sealed chamber for the displacement fluid. Then the pipette tip with the deformation section can be inserted into the receptacle of the displacement device, which exerts a deformation force on the deformation section when the chamber is pressurized with displacement fluid. When the displacement fluid is pressurized by means of the pre-deformation devices, the pipette tip is at the same time fixed in the receptacle, the walls of which are narrow apply to the deformation section. So that the chamber pressure primarily causes a deformation of the receptacle with the deformation section used, the displacement device is preferably supported on the outside in the housing on rigid contact surfaces. If the chamber extends around the receptacle in its insertion direction, maximum deformability of the deformation section is ensured perpendicular to its insertion axis or in the radial direction.

To compensate for dosing errors due to material deformation and for reproduced sample dosing, the deformation section and / or the displacement device can consist of incompressible and / or elastic material. For the displacement device, in particular rubber or other chemically stable and aging-insensitive material can be considered. The pipette tip is preferably made of a polyolefin, which due to its elasticity enables reversible reshaping.

In order to further avoid undesired contamination, a dropper can engage the pipette tip, which can be actuated by means of a dropping process and, when actuated, shifts the pipette tip into a release position. When the throwing member is actuated, a Avoid contact with the pipette tip. The ejector preferably engages under the ring flange of the pipette tip with a ring section, so that a secure transfer is ensured.

Fig. 1

eine herkömmliche Kolbenhubpipette mit aufsteckbarer Pipettenspitze in Seitenansicht;

Fig. 2 und 3

eine herkömmliche Kolbenhubpipette mit aufsteckbarer Kapillarpipettenspitze in Seitenansicht und in ausschnittsweiser Vergrößerung des Spitzenbereichs;

Fig. 4

eine erfindunsgemäße Pipettiervorrichtung in Seitenansicht und teilweisem Längsschnitt durch den Aufnahmebereich für die Pipettenspitze;

Fig. 5 und 6

eine einteilig ausgebildete Pipettenspitze der erfindungsgemäßen Vorrichtung im teilweisen Längsschnitt und in verkleinerter Seitenansicht;

Fig. 7 und 8

eine erfindungsgemäße Pipettiervorrichtung mit einstellbarer Hubbegrenzung und koaxialer Kolbeneinheit mit Kurvenscheibensteuerung im Längsschnitt und einer Seitenansicht des Oberbereichs;

Fig. 9

eine erfindungsgemäße Pipettiervorrichtung mit druckstangengesteuerten Kolben im Längsschnitt;

Fig. 10

eine Kolbensteuerung derselben Pipettiervorrichtung in vergrößerter Perspektivansicht;

Fig. 11

eine erfindungsgemäße Pipettiervorrichtung mit gegenüber Fig. 9 und 10 geändertem Abwerfer im Längsschnitt;

Fig. 12

eine erfindunsgemäße Pipettiervorrichtung mit parallel angeordneten Kolben und Dosierhebel im Längsschnitt;

Fig. 13

einen Teilschnitt durch den Aufnahmebereich mit der Pipettenspitze einer erfindungsgemäßen Pipettiervorrichtung in verschiedenen Arbeitsphasen;

Bei der Beschreibung der verschiedenen Pipetten werden für die Teile gleicher Benennung identische Bezugsziffern verwendet.Further details and configuration of the subject matter of the invention result from the following description of the associated drawings, which show preferred configurations. The drawings show:

Fig. 1

a conventional piston pipette with attachable pipette tip in side view;

2 and 3

a conventional piston pipette with attachable capillary pipette tip in side view and in a partial enlargement of the tip area;

Fig. 4

an inventive pipetting device in side view and partial longitudinal section through the receiving area for the pipette tip;

5 and 6

a one-piece pipette tip of the device according to the invention in partial longitudinal section and in a reduced side view;

7 and 8

a pipetting device according to the invention with adjustable stroke limitation and coaxial piston unit with cam disk control in longitudinal section and a side view of the upper area;

Fig. 9

a pipetting device according to the invention with plunger-controlled pistons in longitudinal section;

Fig. 10

a piston control of the same pipetting device in an enlarged perspective view;

Fig. 11

a pipetting device according to the invention with a modified ejector in relation to FIGS. 9 and 10 in longitudinal section;

Fig. 12

a pipetting device according to the invention with pistons and metering lever arranged in parallel in longitudinal section;

Fig. 13

a partial section through the receiving area with the pipette tip of a pipetting device according to the invention in different working phases;

When describing the different pipettes, identical reference numbers are used for the parts with the same name used.

Conventional pipettes according to FIGS. 1 to 3 have a connection attachment 2 at the front end of a housing 1, onto which a pipette tip 3 with an enlarged end is inserted. 1, a working volume is accommodated in the housing 1, which communicates with the pipette tip 3 and its tip opening 4 through the connection attachment 2. In order to protect the working volume from contamination, a filter can be arranged in the transition area between the connection attachment 2 and the pipette tip 3.

2 and 3, the working volume 5 is in the capillary pipette tip 3 and is limited to the housing 1 by a piston 6 on a thin piston rod 7. Both devices still leave something to be desired in terms of their handling and freedom from contamination.

4, the invention provides a pipette tip 3 which has a working volume 5 in a deformation section 8 with a cylindrical shape, which is closed in a bubble-like manner. The deformation section 8 has a curved end region 8 'at one end and a curved transition region 8''at the other end. The transition region 8 ″ leads to a tip section 3 ′ of the pipette tip 3, which is tapered towards the tip opening 4. Air or sample material can thus only get into or out of the tip through the tip opening 4.

The deformation section 8 is held in the housing 1 in a complementarily shaped receptacle 10 of a displacement device 11. The displacement device 11 consists of a rubber-elastic and thus incompressible material which is supported circumferentially and end-walled on the housing walls. The displacement device 11 not only serves to hold the pipette tip 3, but is part of an actuating device. For this purpose, it has an annular chamber 12 adjacent to the surrounding wall of the housing 1, which extends in the longitudinal direction of the pipette tip 3 and is connected via a channel 13 to hydraulic devices of the actuating device to be discussed below.

By applying pressure by means of the hydraulic devices, the inner walls of the chamber 12 can be deformed towards the longitudinal axis of the pipetting device, whereby they radially compress the deformation section 8. Thus, the hydraulic medium can hold the pipette tip 3 in place in the receptacle 10 by slight pretensioning and eject one in the pipette tip by further increasing the pressure contained fluids are caused. When the pressure is reduced, the displacement device 11 and the deformation section 8 deform elastically back, the pipette tip 3 sucking in through its tip opening 4. The pipette tip 3 can be released by completely reducing the hydraulic pressure in the chamber 12.

5 and 6 show a pipette tip 3, the conical tip section 3 'and cylindrical deformation section 8 are integrally connected to one another in the flange 14. This generally requires the pipette tip 3 to be made entirely of deformable material, in particular a deformable plastic. Polypropylene and / or polyethylene are particularly suitable as materials for the pipette tips 3 according to FIGS. 4 to 6.

In the case of a pipetting device according to FIGS. 7 and 8, the housing 1 accommodates a pipette tip 3 at the lower end in a displacement device 11 similar to that of FIG. 4. A cylinder block 15 is adjacent to the displacement device 11. This contains a cylinder (not shown) for a metering piston 16 and a pre-deformation piston 17 surrounding it coaxially. According to FIG. 4, the cylinder is connected to a chamber 12 of the displacement unit 11 via a channel 13.

The metering piston 16 is guided in the upper region by a guide plate 18 which is supported on the housing side. Between a plate 19 at the upper end of the metering piston 16 and the guide plate 18, a spiral spring 20 is held, which tries to push the metering piston 16 out of the cylinder as much as possible while reducing the hydraulic pressure.

On the other side of the plate 19, a push rod 21 is supported, which is guided by a stroke limiter 22. It has a stop flange 23 which is movable between end stops 24, 25 of the stroke limiter 22. The latter end stop 25 is designed as an overstroke stop in that it is movable relative to a sleeve-shaped jacket section 26 of the stroke limiter 22. The overstroke stop 25 is supported by a further coil spring 27 on a further guide plate 28 fixed on the housing side, which at the same time centers the push rod 21. If the stop flange 23 reaches the overstroke stop 25 against the action of the spiral spring 20 when a push button 29 is actuated, then it can be displaced further against the additional effect of the spiral spring 27. As a result, the metering piston 16 is informed of a further movement distance, the function of which will be discussed further below.

The path of the metering piston 16 is also variable by changing the position of the upper end stop 24 for the stop flange 23. This enables the pipetting volume to be adjusted, which is already known in principle. For this purpose, the upper end stop 24 has a square 30 outside the stroke limiter 22, which is guided through a square seat of a spur gear 31. The spur gear 31 is rotatable in the housing 1, but is arranged so as not to be displaceable in the longitudinal direction. It meshes with a helical gear 32 which is arranged on an adjusting shaft 33 which carries adjusting knobs 34 outside the housing. In addition, the helical gear 32 drives a counter 34, which has a display 35 visible from the outside.

Rotation of an adjusting knob 34 for the purpose of changing the pipetting volume causes the spur gear 31 and thus the end stop 24, which is held on an adjusting thread 36 in the stroke limiter 22, to rotate via the helical gear 32. As a result, the end stop 24 is axially displaced, whereby it slides with its square 30 in the square receptacle of the axially held spur gear 31. As a result of the action of the spiral spring 20, the push rod 21 and the metering piston are held in contact with the end stop 24 when the pushbutton 29 is not under load, so that when the pushbutton is actuated a different one Pipetting volume is available.

The pre-deformation piston 17 is provided with a plate-shaped pressure plate 37 at the upper end. Between this and the cylinder block 15, another spiral spring 38 is supported, which presses the pre-deformation piston 17 out of the cylinder block 15 as far as possible. It forces the pressure plate 37 to rest on an arrangement with cams 39 which are arranged on both sides of the metering piston 16. The cam discs 39 are connected in a rotationally fixed manner to a spur gear 41, which meshes with a longitudinal toothing 42 of a slide 43.

By moving the slide in the longitudinal direction of the pipette away from the pipette tip 3, the spur gear 41 and the cam plate 39 are driven in a clockwise direction. The eccentricity of the cam plate 39 causes the pre-deformation piston 17 to be pressed into the cylinder block 15. As a result, the hydraulic pressure within the chamber of the displacement unit 11 is increased somewhat, as a result of which the pipette tip 3 is somewhat compressed at the deformation section and is thereby retained. The contour of the cam plate 39 ensures that self-locking of the pre-deformation drive occurs in the case of pre-deformations and the position of the preforming piston 17 is retained during subsequent pipetting processes.

Furthermore, an ejector 44 is arranged at the lower end of the pipetting device, which engages under the ring flange 14 of the pipette tip 3 with a ring section 45. A rod section 46 of the ejector 44 is guided in the housing 1 up to the lower edge of the slide 43. A movement of the slide 43 towards the pipette tip thus not only releases the pipette tip 3 as a result of the opposite movement of the pre-deformation piston 17, but also shifts the ejector 44 in the direction of the pipette tip 3 so that it is pushed off the front end of the pipetting device.

The pipetting device according to FIGS. 9 and 10 is only discussed below with regard to features that are additionally shown compared to FIGS. 7 and 8 or are present in deviation.

Also shown here is a liquid-tight plug connection 47 between the displacement device 11 and the cylinder block 15, which contains a passage channel 48 for hydraulic fluid from the cylinder 49. This illustration can also be seen, like metering piston 16 and pre-deforming pistons 17 engage together in the cylinder 49 and are sealed against this and against one another by means of O-rings 50, 51.

A distinguishing feature is that the metering piston 16 is formed in one piece with the push rod 21 and is fixed in the push button 29. As a result, the coil spring 20 is also arranged elsewhere, namely between the push button 29 and the pot-shaped spur gear 31, which is supported in the longitudinal direction. As a result, the metering piston 16 is also pulled out of the cylinder 49 or the preforming piston 17 as far as the position of the push button 29 allowed.

The slide 43 is also designed differently. As can be seen in particular from FIG. 12, it has locking pegs 52 on both sides on a common axis, which are guided in a rail (not shown) of the housing 1. At the bottom, it is connected to a pressure rod 54 via an articulated connection 53. Hinge bolts of the hinge connection 53 can also protrude into the housing rails. The pressure rod 54 is also provided at the bottom with guide pins 55 on both sides, which engage in the housing rails. At the bottom he also has two spherical support surfaces 56, which are on the Support pressure plate 37 for the pre-deformation piston. Slider 43 and pressure rod 54 are hollow, the latter consisting essentially of two side parts with an eyelet 57 holding them together. The metering piston 16 is guided through the cavities of the slide 43 and the pressure rod 54.

To pre-deform an inserted pipette tip by increasing the pressure of a hydraulic medium, the slide 43 must first be pushed in the direction of the pipette tip. The locking pins 52 and 56 slide in the housing rails until the upper locking pins 52 reach a locking recess in the rails. Then the slide 43 can be pivoted about the pivot point of the articulated connection 53 with the latching pins 52 into the latching recess, the push rod 54 being essentially aligned with the longitudinal axis of the pipette due to its guide pin 55, possibly further guide pins of the articulated connection 53 or a lateral support in the housing 1 remains. A certain angle attachment is compensated for by the spherical end faces 56, which roll on the pressure plate 37. In this latching position, the pre-deformation piston 17 is pressed and fixed in the cylinder 49 in such a way that the pre-deformation section of the pipette tip is sufficiently radially compressed.

Finally, in this pipetting device, another ejector 44 with a ring section 45 is provided, a somewhat extended ejector rod 46 being guided to a sliding ejector member 58.

The pipetting device according to FIG. 11 differs from that in FIGS. 9 and 10 essentially by the ejector mechanism, the ejector rod 46 extends to the push button 29 and is connected there to a push button-like ejector 59. The latter has a blind bore 60 for improved degree guidance, which is aligned with a pin bore 61 of the housing 1 for a guide pin (not shown). For the sake of clarity, the spiral spring for the return of the pistons 17, 16 and the overstroke stop 25 have also been omitted in this drawing.

The pre-deformation mechanism of this version corresponds to that according to FIGS. 9 and 10, the slide 43 being shown in the pivoted latching position. The drawing demonstrates that this does not affect the alignment of the push rod 54 along the longitudinal axis.

The pipetting device in FIG. 12 has one in the housing 1 adjacent to the displacement device 11 Cylinder block 15, which is equipped with two - not shown - cylinders. In the drawing on the right, a metering piston 16 engages in a cylinder, which is provided at the top with a plate 19 for supporting a prestressing spiral spring 20. 9, a push rod 21 is supported on the plate 19, which is guided by a stroke limiter 22. However, the stroke limiter 22 has fixed end stops, so that neither an overstroke nor a change in the pipetting volume are possible.

A one-sided dosing lever 62 is provided for actuating the dosing piston 16, the bearing 63 of which is arranged on the side of the housing 1 opposite its housing outlet. Its housing outlet is protected from the ingress of foreign bodies by means of a roller cover 64. The metering lever 62 is guided past the push rod 21 and stroke limiter 22 on both sides with two parallel lever sections, these arm sections articulatedly supporting a drive yoke 65, which likewise has side parts arranged on both sides of the push rod 21. The side parts are connected at the top by means of a cross piece 66, which has a spherical shell 67 for receiving a spherical head 68 at the upper end of the push rod 21.

When the metering lever 62 is actuated in the direction of an inserted pipette tip 3, the drive yoke 65 pulls the push rod 21 downward, which influences the hydraulic pressure in the displacement unit 11 via the metering piston 16. The joints on both ends of the drive yoke 65 compensate for an angular offset.

In the drawing on the left, a pre-deformation piston 17 is guided into the cylinder block 15 and is supported parallel to the metering piston 16. At the top, the pre-deformation piston 17 carries a plate 37, a spiral spring 38 being arranged between the plate and the cylinder block. The latter also ensures that the pre-deformation piston 17 is pulled out of the cylinder block 15 as far as possible.

The plate 37 also forms a pressure rod and has an articulated connection 53 to a slide 43 at the top, the laterally protruding articulated bolts are guided in rails of the housing 1. The slide 43 also projects into the housing rails with locking pins 52 on both sides. If it is pushed towards the pipette tip 3 in the direction of the longitudinal axis of the pipette, the locking pins 52 finally reach a locking recess in the housing rails, in which they can be locked by pivoting the slide 43 are. Then the pre-deformation piston has reached a position in which a sufficient hydraulic pressure is reached in the associated cylinder, which, like the cylinder for the metering piston 16, is connected to the chamber of the deformation device 11 via a hydraulic channel.

In this version, a ring section 45 of an ejector 44 also engages a ring flange of the pipette tip 3. An ejector rod 46 is guided up to the vicinity of the upper end of the pipetting device, where it is connected to an ejector slide 69. In this version, the actuating elements are arranged ergonomically in a particularly favorable manner.

FIG. 13 shows the contamination-free pipetting device in different working phases, which are identified with Arabic numerals. In working phase 1, a pipette tip 3 is inserted into the receptacle 10 of the displacement device 11. Phase 2 denotes the tensioning of the pipette tip 3 by pre-deforming the deformation section 8 in the radial direction inwards. Phase 3 symbolizes the displacement of the dosing volume from the pipette tip 3 by further deformation of the deformation section 8 and the working volume 5, which is expedient when the tip opening 4 is immersed. In phase 4 the liquid absorption has already been completed, the deformation section 8 being partially deformed back. Partial representation 5 is dedicated to the dispensing of liquid into a provided receptacle, which is associated with renewed compression of the deformation section 8 and working volume 5, including an overstroke. Finally, phase 6 shows the pipette tip 3 after complete relaxation of the displacement unit 11 and phase 7 the ejection process, which is associated with a displacement of the ejector 44.

Claims (19)

Pipetting device with a housing (1) and a receptacle (10) formed therein, a pipette tip (3), which has a tubular tip section (3 ') with a tip opening (4) for fluid passage from the outside inwards and vice versa, and thus forms one unit connected deformation section (8), the pipette tip (3) with outwardly projecting tip section (3 ') inserted into the receptacle (10) and detachably connected to the housing (1), an actuating device (29) and an actuating device coupled to it (11, 15, 16, 21), which rests on the outside of the deformation section (8) in order to compress or relax this and a working volume (5) arranged therein to the tip opening (4) in accordance with an actuation of the actuating device (29), thereby characterized in that the inside width of the undeformed deformation section (8) exceeds that of the tip opening (4) and the adjusting device (11, 15, 1 6, 21) the deformation section (8) is deformed essentially in the transverse direction over the entire deformation region of the working volume (5). Device according to claim 1, characterized in that the deformation section (8) has a bubble-like, cylindrical and / or bellows-like shape. Device according to claim 2, characterized in that the cylindrical deformation section (8) has a curved end region (8 ') at one end and a curved transition region (8' ') at the other end to the tip section (3'). Device according to one of claims 1 to 3, characterized in that the pipette tip (3) has a conical tip section (3 '). Device according to one of claims 1 to 4, characterized in that the pipette tip (3) between the deformation section (8) and tip section (3 ') has an annular flange (14). Device according to one of claims 1 to 5, characterized in that the receptacle (10) has an opening for the axial insertion of the deformation section (8) and an inner contour corresponding to the outer contour of the inserted deformation section. Device according to one of claims 1 to 6, characterized characterized in that the adjusting device has a metering cylinder (49) with a metering piston (16) guided therein and displaceable by means of the actuating device (29) for deforming the deformation section (8). Apparatus according to claim 7, characterized in that the actuating device (29) is coupled to the metering piston (16) via a linkage (21), that the linkage (21) has a stroke limiter (22) which has a stop flange (23) fixed to the linkage and Has end stops (24, 25) fixed on the housing side at a distance from one another on both sides of the stop flange, and that the distance between the end stops (24, 25) is variable by means of an actuating gear (31, 32, 22, 24). Device according to one of claims 1 to 8, characterized in that the actuating and adjusting devices have pre-deformation devices (43, 17) for pre-deforming the deformation section (8). Apparatus according to claim 9, characterized in that the pre-deformation devices have a pre-deformation piston (17) for pre-deforming the deformation section. Apparatus according to claims 6 and 10, characterized in that the pre-deformation piston (17) and the metering piston (16) are guided in parallel next to one another in a pre-deformation cylinder and a metering cylinder. Device according to one of the preceding claims and claims 6 and 14, characterized in that the pre-deformation piston (17) and metering piston (16) are arranged coaxially in a common cylinder (49). Device according to one of claims 6 to 12, characterized in that metering pistons (16) and / or pre-deformation pistons (17) act on the deformation section (8) via a displacement fluid. Device according to one of claims 1 to 13, characterized in that the adjusting device has a displacement device (11) made of flexible material, with a receptacle (10) for the deformation section (8) and at least one chamber (12) for the displacement fluid. Device according to claim 14, characterized in that the displacement device (11) is supported on the outside in the housing (1) on rigid contact surfaces. Apparatus according to claim 14 or 15, characterized in that the chamber (12) extends around the receptacle (10) in the direction of insertion. Device according to one of claims 1 to 16, characterized in that the deformation section (8) and / or displacement device (11) consist of incompressible and elastic material. Device according to one of claims 1 to 17, characterized in that an ejector (44) acts on the pipette tip (3), which can be actuated by means of an ejector member (43, 58, 59) and moves the pipette tip into a release position when actuated. Device according to Claims 5 and 18, characterized in that the ejector (44) engages under the ring flange (14) of the pipette tip (3) with a ring section (45).

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