EP1862219B1 - Device for holding a pipette tip and pipetting device - Google Patents

Description

The invention is in the field of dosing and relates to a device for holding and positioning of pipette tips and a pipette tip.

Pipette tips are elongate, typically tapered, sleeves having a central passageway along the longitudinal axis for metering small quantities of fluid. The pipette tips are pushed at their wider end (coupling end) on a suitable holder of a pipetting device and immersed with its pointed end which is axially opposite the wide end in the medium to be pipetted. Typically, the pipette tips are for single use, i. that they are thrown away after use.

Pipetting devices are widely used everywhere where relatively small amounts of liquid (for example in the microliter range) have to be dosed, for example in molecular biology. The pipetting device may be manual pipetting devices or pipetting or pipetting robots having a single pipetting unit or a plurality of individual pipetting units operated simultaneously or separately.

The basic mode of operation of a pipetting device is based on the fact that a defined volume of fluid is displaced eg in a cylinder. The cylinder is connected on the output side airtight with the passage opening of the pipette tip, so that the displacement of the fluid volume causes a corresponding volume of the medium to be pipetted is sucked at the tip end of the pipette tip. To ensure accurate dosing, the pipette tip must be securely and tightly connected to the pipetting device. This is required to a greater extent in automatic pipetting machines in which the secure seating and precise positioning of the individual pipette tips can not be checked manually. In addition, pipetting devices should be as low maintenance and inexpensive to produce.

There are a number of pipetting devices with holding devices for receiving pipette tips known. For example, describe US 2002/094302 . U.S. 4,679,446 . DE 197 08 151 and US 4,748,859 Pipette tips having integrally formed circumferential sealing bands on the inner wall of their coupling end which radially seal the pipette tip to an outer peripheral surface of the holder. As a result, a lateral position alignment of the pipette tip is to be achieved at the same time.

Elaborate radial seals are also in US 2003/219359 and US 2004/011145 described. These seals consist of molded on the inner wall of the pipette tip sealing lips, which should nestle against an outer peripheral surface of the holder. However, the production engineering effort to produce the sealing lips is relatively high. In addition, the lateral fit of the pipette tip with sealing lips can not be sufficiently ensured.

For axial alignment of the pipette tips, ie in the z-direction, additional axial alignment can be provided. These are eg in US 6,168,761 . US 2003/082078 . CA 2 122 244 . US Pat. No. 6,248,295 . EP 148 333 . US 6,973,845 and US 4,824,641 described.

All of the aforementioned pipette tips are held by the pinch seal of the circumferential seal on the outer peripheral surface of the holder. A fixation with separate locking ribs, however, shows US 5 200 151 , which are integrally formed on the inner wall of the passage opening of the pipette tip and engage behind a circumferential on the outer peripheral surface of the holder latching holder.

A holding device with a rigid sealing bead is in US 2003/0000319 described. This sealing bead cooperates in the radial direction with a sealing surface of a pipette tip, wherein the wall thickness of the pipette tip in the region of the sealing surfaces is sufficiently thin to ensure easy stretching when pushed onto the sealing bead.

A radial seal between pipette tip and fixture is in EP 0 351 574 described. There, the holding device has a cylindrical sealing section which corresponds to a sealing section of the pipette tip, the wall thickness in the area of the pipette tip-side sealing section being smaller and thus flexible compared to adjacent areas. This is achieved by a wall thickness weakening on the inside and outside of the pipette wall. A pipette tip with elastic cylindrical sealing portion is also in WO 00/27530 described.

Out WO 00/62933 For example, a pipetting device is known which has an annular pinch seal for radially sealing the pipette tip. For sealing a displaceable ferrule is pressed axially on the annular pinch seal and this pressed radially outwardly into an annular groove which is formed on the inner wall of the passage opening of the pipette tip. A coupling sleeve with an annular stepped shoulder is arranged upstream of the pinch seal axially in the direction of the pipette tip, which serves for the axial and radial positioning of the pipette tip. In the pipetting device of WO 00/62933 the pipette tip is held and sealed by the pinch seal, which, however, requires moving elements to operate it. This leads to a higher maintenance and equipment costs. In addition, the pinch seal is subjected to increased wear due to the required flexing work.

• ein Dichtelement aus einem elastischen Material, das einen in axialer Richtung zum freien Ende des Koppelelements hin freiliegenden axialen und sich radial ersteckenden Dichtabschnitt aufweist, gegen den ein Dichtabschnitt der Pipettenspitze zumindest teilweise axial preßbar ist.

Against this background, therefore, the invention has for its object to provide a device for holding pipette tips or corresponding pipette tips, with which an accurate dosing is possible and preferably improved compared to the prior art product properties in terms of wear, maintenance and have the production costs. The invention therefore proposes a device for holding pipette tips with a coupling element having a longitudinal axis extending in the axial direction, which has a free end from which a pipette tip can be pushed onto the coupling element in the axial direction, wherein the coupling element has:

• a sealing element made of an elastic material which has an axial and radially ersteckenden sealing portion exposed in the axial direction to the free end of the coupling element, against which a sealing portion of the pipette tip is at least partially axially pressed.

According to one aspect of the invention, the coupling element may further comprise at least one guide element arranged on its outer side for aligning the pipette tip laterally with respect to the longitudinal axis.

According to a further aspect of the invention may be arranged on the outside of the coupling element, a holding element for interacting with holding means of the pipette tip to press the sealing portion of the pipette tip against the axial sealing portion and to position the pipette tip in the axial direction.

The pipette tip is sealed according to the invention by an axially acting seal on the coupling element. For this purpose, the coupling element on an elastic sealing element, against which a sealing portion of the pipette tip can be axially pressed. The advantage of an axial seal is that it is significantly less susceptible to wear than a radial seal. A radial seal must be rubbed over an outer peripheral surface of the support until it is sufficiently crimped and sealed, or, as in the pinch seal described above WO 00/62933 , is subjected to a great flexing work. In contrast, in the case of an axial seal, the corresponding sealing section only needs to be pressed against the seal. The holder of the invention is thus considerably more durable and low maintenance. The sealing element consists of a material which is more elastic in comparison to the material of the coupling element and has a better elastic deformability. The sealing element has an axial sealing section, ie a section accessible from the axial direction, for example an end face against which the sealing section of the pipette tip can be pressed axially.

Furthermore, the gasket and fixture are advantageously separated both spatially and functionally, i. Sealing and holding element are designed as separate elements. The sealing element seals the pipette tip on the coupling element. Moreover, due to the axial sealing effect, it also serves as an axial positioning means. However, the pipette tip is not held or fastened by the seal. This function takes over the holding element, which interacts with an associated holding means on the pipette tip and secures this against axial displacement. At the same time the sealing portion of the pipette tip is pressed against the axial sealing portion of the sealing element and on the one hand reaches the desired sealing effect and on the other hand defines the axial position of the pipette tip by the holding element and sealing element. The holding element allows a detachable connection between coupling element and pipette tip.

Finally, the lateral or radial alignment of the pipette tip on the coupling element is advantageously ensured by cooperation of the holder-side guide element with corresponding guide elements, typically cylindrical surfaces on the inner wall of the pipette tip.

The separation of sealing and holding function as well as lateral guidance is particularly advantageous in pipetting machines, since it makes it possible to precisely define the axial alignment (z position) through the interaction of the axial seal and holding element. On the other hand, a radial pinch seal could prevent a defined axial positioning. Furthermore, the mounting device according to the invention has a low-wear seal and allows accurate positioning of the pipette tip and their secure support.

• eine um eine Längsachse verlaufende Mantelfläche;
• einen Koppelabschnitt in der Nähe eines ersten axialen Endes der Pipettenspitze,

das in Aufschiebrichtung der Pipettenspitze angeordnet ist, wobei der Koppelabschnitt mindestens einen Abschnitt mit einer entgegen der Aufschiebrichtung zumindest abschnittsweise konisch zulaufenden Innenwand hat, in die eine in bezug auf die Längsachse zylindrische Führungsfläche integriert ist.The invention further relates to a pipette tip for placement on a holder, wherein the pipette tip has:

• a circumferential surface extending about a longitudinal axis;
• a coupling portion near a first axial end of the pipette tip,

which is arranged in the sliding direction of the pipette tip, wherein the coupling portion has at least one portion with an opposite to the Aufschiebrichtung at least partially conically tapered inner wall into which a cylindrical with respect to the longitudinal guide surface is integrated.

The integrated cylindrical guide surface should preferably run longitudinally parallel to the longitudinal axis. This ensures that the pipette tip assumes a defined radial position in interaction of its guide surface with a guide element of the holder regardless of its axial position. The pipette tip can therefore be pushed onto the holder without the guide surface hindering an axial relative movement of the pipette tip and the holder with respect to one another. The guide surface therefore only results in a radial alignment of the pipette tip without affecting its axial positioning, i. axial and radial alignment are separated.

The inner wall has in the longitudinal axis direction with respect to the longitudinal axis typically at an angle greater than or equal to 0.2 °, preferably between 0.5 ° and 3 °, in particular between 0.5 ° and 1 °. Due to the relatively low angle, the inner wall is formed as Entformungsschräge for easier removal of the prepared pipette tip from an injection mold at a comparatively small taper of the hollow cross-section.

The coupling section may furthermore have a first section and a second section axially staggered with respect to the first section in the sliding direction, the first section having a smaller radial extent than the second section. In addition, the coupling section may have a sealing section between the first and second sections with a sealing surface facing axially in the sliding direction for interacting with a sealing element of the holder and one on the inner wall of the second section arranged holding means for interacting with a holding element of the holder.

The retaining means may be an undercut formed on the inner wall of the second section. Typically, the pipette tip is an injection molded part, with the inner walls of the first and second portions being parallel to the longitudinal axis, i. have no draft angles. Furthermore, the coupling portion, and in particular the second portion of the pipette tip, comprise a region which is made more flexible with respect to the remaining regions of the coupling portion or the second portion and is arranged towards the first axial end. The flexible area facilitates the placement and stripping of the pipette tip from the holder. In order to improve the flexibility and to selectively adjust it is possible to provide in the coupling section or in the second section of the coupling section in the longitudinal direction incisions and to fill them with a second material that is more elastic than the material from which the remaining areas of the coupling portion or of the second section. The coupling section therefore consists of different materials.

The sealing portion may be formed by a shoulder or shoulder between the first and second portions.

• zwei axial voneinander beabstandete Führungselemente, und
• ein in bezug auf die Führungselemente separates Halteelement zum Wechselwirken mit Haltemitteln der Pipettenspitze, um die Pipettenspitze in axialer Richtung zu positionieren.

According to a further aspect, a device for holding pipette tips is proposed with a coupling element having a longitudinal axis extending in the axial direction, which has a free end from which a pipette tip on the coupling element in the axial direction can be pushed, wherein the coupling element on its outside having:

• two axially spaced guide elements, and
• a separate with respect to the guide elements holding member for interacting with holding means of the pipette tip to position the pipette tip in the axial direction.

The holding element may be a flexible element, which is suitably mounted on the outside of the coupling element, or integrally formed on the outside or be separately attached to the outside rigid or elastic element, for example, one or more radial projections, which are partially or annular circumferentially distributed.

According to a further aspect, a pipetting device with a coupling element and a detachable attachable to the coupling element pipette tip is proposed with a sealing portion, wherein the coupling element has an axially extending longitudinal axis and has a free end, from which the pipette tip on the coupling element in the axial direction pushed is. The coupling element further has a sealing element made of an elastic material which has an axial and radially extending sealing section exposed in the axial direction towards the free end of the coupling section. The sealing portion of the pipette tip, however, is preferably designed with respect to the longitudinal axis of the coupling element as an axial surface facing in the direction of the coupling element, and can be formed for example by a shoulder. In the coupled state, at least a part of the sealing portion of the coupling element should be axially pressed against at least a portion of the sealing portion of the pipette tip. The coupling element of the pipetting device may additionally individually or in combination, the properties of the above-described separate coupling element, for example, in view of the properties and the material of the sealing element, the number, design and arrangement of guide elements or the number, design and arrangement of holding elements.

According to a further aspect, a pipetting device with a coupling element and a pipette tip detachably attachable to the coupling element is proposed, wherein the coupling element has at least one guide element arranged on its outside for laterally aligning the pipette tip, and preferably comprises as many guide elements as the pipette tip has guide surfaces. The one or more guide element (s) may be formed independently of one another preferably in one piece or in several parts. The pipette tip has a longitudinal axis and a coupling section extending in the longitudinal axis for pushing onto the holder. The coupling section further has at least one section with an inner wall tapering at least in sections opposite the direction of slipping into which a guide surface which is cylindrical relative to the longitudinal axis is integrated for interacting with the at least one coupling-side guide element. The one or more guide element (s) on the coupling element is (are) designed so that each guide element has at least partial surfaces of a cylindrical lateral surface which corresponds in each case to an interacting with the partial surface cylindrical guide surface on the pipette tip. In addition, the pipette tip can individually or in combination have the properties of the separate pipette tip already described above, for example with regard to the properties, the material, the configuration and arrangement of the inner wall, special sections or holding elements. In addition, the coupling element of the pipetting device can also here additionally or individually in combination have the properties of the above-described separate coupling element, for example with regard to the number, configuration and arrangement of guide elements. In addition, the coupling element may comprise a sealing element with properties, configurations and suitable materials already described above and one or more holding elements already described above with regard to number, configuration and arrangement.

The coupling element can furthermore have at least one holding element arranged on its outside for interacting with at least one holding means of the pipette tip. In this case, the at least one holding element can be designed to be rigid relative to the at least one holding means. Alternatively, the at least one holding element can also be designed to be flexible with respect to the at least one holding means.

• Figur 1 eine Schnittansicht einer Halterung mit Koppelelement und Pipettenspitze gemäß einer ersten Ausführungsform;
• Figur 2 eine Schnittansicht einer Halterung mit Koppelelement und aufgeschobener Pipettenspitze gemäß der ersten Ausführungsform;
• Figur 3 eine Schnittansicht einer Halterung mit Koppelelement und aufgeschobener Pipettenspitze gemäß einer zweiten Ausführungsform;
• Figur 4 ein Ausschnitt eines Koppelelements mit X-förmigem Dichtelement;
• Figur 5 eine Schnittansicht einer Halterung mit Koppelelement gemäß einer dritten Ausführungsform;
• Figur 6 einen ersten Ausschnitt vom Koppelelement gemäß drittem Ausführungsbeispiel;
• Figur 7 einen zweiten Ausschnitt vom Koppelelement gemäß drittem Ausführungsbeispiel;
• Figur 8 ein Koppelabschnitt eines ersten Ausführungsbeispiels einer Pipettenspitze; und
• Figur 9 ein zweites Ausführungsbeispiel einer Pipettenspitze.

In addition, the invention will be explained with reference to embodiments shown in FIGS form, which results in further advantages and modifications. To show:

• FIG. 1 a sectional view of a holder with coupling element and pipette tip according to a first embodiment;
• FIG. 2 a sectional view of a holder with coupling element and deferred pipette tip according to the first embodiment;
• FIG. 3 a sectional view of a holder with coupling element and deferred pipette tip according to a second embodiment;
• FIG. 4 a section of a coupling element with X-shaped sealing element;
• FIG. 5 a sectional view of a holder with coupling element according to a third embodiment;
• FIG. 6 a first section of the coupling element according to the third embodiment;
• FIG. 7 a second section of the coupling element according to the third embodiment;
• FIG. 8 a coupling portion of a first embodiment of a pipette tip; and
• FIG. 9 A second embodiment of a pipette tip.

Special holders are used for secure attachment and holding of pipette tips to pipetting devices or pipetting machines. The holder according to the invention has for this purpose a coupling element with a particular cylindrical base body, which comprises an elastic sealing element with axially exposed in the direction of the free end of the holder and at least partially radially extending sealing portion. Against this sealing portion can be pushed axially a corresponding sealing portion of a pipette tip. The sealing effect is achieved by axial pressing against the sealing element. Typically, the sealing element consists of a fluoroelastomer and can be embodied for example as an O-ring or as an X-ring, where O and X refers to the cross section of the ring material. Other cross sections, such as hollow or V cross sections are also possible. By choosing the respective cross-section, a material elasticity in cross section is to be achieved, i. the cross section of the sealing element is elastic, in particular deformable in the longitudinal direction of the coupling element, and therefore allows a very good axial sealing effect.

The coupling element furthermore has at least one guide element for lateral positioning and alignment of the pipette tip with respect to the longitudinal axis of the holder. In particular, the guide element can be formed radially, preferably with a constant radial extent around the coupling element, wherein it may consist of sub-elements. In this case, the guide element project radially beyond adjacent sections of the outside of the coupling element. The guide element thus has a greater radial extent than adjacent portions of the coupling element. This ensures that a radial contact between the coupling element and the pipette tip is produced essentially only via the guide element and thus the guide element determines the lateral or radial position of the pipette tip. Typically, the guide element bears against the inner wall of the pipette tip, which in turn may have corresponding guide elements or guide surfaces. The guide element can be annular. The holder-side guide element is, in particular, cylindrical guide surfaces or partial surfaces with respect to the longitudinal axis of the coupling element. Thus, unlike conical surfaces, the lateral guidance and orientation of the pipette tip is independent of axial positioning means.

In one embodiment of the holder according to the invention, the coupling element may have two axially spaced-apart guide elements on its outer side. As a result, the lateral or radial alignment or positioning of the pipette tip is further improved. Likewise, an improved coaxial alignment of coupling element and pipette tip is achieved, i. that a tilting or oblique holding the pipette tip is prevented on the holder. This is particularly advantageous in pipetting machines with a large number of simultaneously actuated pipette tips, which are arranged in a matrix, for example.

It is favorable if both guide elements have an axial distance which is at least as great as their greatest radial extent. The axial distance of the guide elements is understood to mean the distance between the contact regions or contact edges which are furthest apart from one another. For example, the guide elements can define guide rings, which run radially around the coupling element and have a different radial extent or different outer diameters. In this case, the axial distance is defined by the respective outer edge or outline of the guide surface, ie the outer edges, which are axially farthest from each other. The guide rings can be designed either as continuous circumferential rings or as interrupted rings. It is also possible to form a guide ring as a continuous circumferential ring and the other guide ring as a broken ring.

The guide element or the guide ring or the guide rings may have a certain axial extent, so that thereby guide surfaces are defined whose axial width substantially corresponds to the axial extent of the guide rings and the guide element. It is also possible to reduce the axial extent of the guide element or the guide rings or the extent that a substantially linear contact between the guide element and the pipette tip remains.

Typically, the coupling element has two guide elements with different radial extent or outer diameter, wherein the axial distance of the two guide elements to each other is at least as large as the larger of the two outer diameter.

In a further embodiment of the invention, the coupling element has a first portion, which is arranged near the free end or at the free end of the coupling element, and a second portion, which is arranged offset axially in the sliding direction to the first portion on. Typically, the sections are substantially cylindrical. Each section may comprise a guide element, wherein in particular the first end facing the free end preferably has at each point a smaller radial extent than the second section. This defines a step between the two sections on which the sealing element can be arranged. The sealing element is therefore preferably between the first and second section and projects beyond in the radial direction typically the first portion and the guide element located there, so that a part of the sealing element is freely accessible axially from the free end of the coupling element ago.

For example, against the sealing element, an inner stepped shoulder of the pipette tip can be pressed, which is formed by a radially encircling and axially facing sealing surface.

The coupling element furthermore has at least one holding element, which is arranged on the outside of the coupling element, interacts with corresponding holding means of the pipette tip and removably fixes the pipette tip. The retaining element causes a particular axial fixation, thereby simultaneously the sealing portion of the pipette tip is pressed axially against the axial sealing portion of the coupling element. In addition, a safe and well-defined axial positioning of the pipette tip is achieved by the interaction of sealing element with sealant on the one hand and holding element and retaining means on the other hand. The holding element may be flexible or rigid.

The retaining element may be a flexible tensioning element, e.g. be a circumferential spring element which is arranged in a located on the outside of the coupling element circumferential recess. Flexible holding elements allow the pipette tip to be pushed on or off with little effort. In addition, flexible holding elements are relatively low wear and relatively fault tolerant because they can compensate for manufacturing tolerances due to their flexibility, for example, the pipette tip partially.

On the other hand, the holding element may also be rigid and, for example, individual radial elevations, for example, rigid cams, which are preferably distributed annularly around the coupling element. Also, a non-annular distribution or a continuous ring are suitable as rigid holding elements. Rigid holding elements have the advantage over flexible holding elements that they allow a more accurate centering of the pipette tip.

Regardless of the specific embodiment of the holding element, this can engage in a radially circumferential undercut on the pipette tip, which is typically arranged on the inner wall of the passage opening of the pipette tip.

In a further embodiment of the invention, the holding element is arranged in the direction of sliding behind the guide elements or arranged. This ensures that the sealing element is in front of the retaining element in the direction of the free end of the coupling element and thereby protects the retaining element against accidental contamination with the medium to be pipetted.

Regarding FIG. 1 Now, a first embodiment will be described. The holding device comprises an axisymmetric, typically substantially cylindrical coupling element 4 with a longitudinal axis 6 and an axially disposed passage opening 5. The coupling element has a front free end 8. From the free end 8, a pipette tip 10 can be pushed onto the coupling element 4. Typically, the pipette tip 10 is formed axially symmetrical and has near its rear end (coupling end and first axial end) 12 a coupling portion 14 which is pushed onto the coupling element 4. The pipette tip runs from its coupling section 14 to its - not shown here - front tip end conically and there has a suction port for sucking the medium to be pipetted.

The pipette tip is typically intended for single use and designed as an injection molded part. A suitable material for pipette tips that is easy to process is polypropylene, which is injected in liquid form and optionally with additives (e.g., paint) and / or fillers into a suitable injection mold. After solidification of the polypropylene, the finished pipette tip is ejected from the injection mold and removed if necessary, the gate.

The coupling element 4 is typically integrally formed from metal and has at its free end 8 a first portion 20. A second portion 22 of the coupling element 4 is arranged axially offset in the sliding direction 2 with respect to the first portion 20. The first portion 20 preferably has at each point a smaller radial extent than the second portion 22, so that the second, in the sliding direction 2 rear portion 22 projects radially beyond the first portion 20. On the outside of each section is in each case a guide element 25, 26 arranged in the form of a circumferential cylindrical guide surface. The guide surfaces 25, 26, which extend in the longitudinal direction parallel to the longitudinal axis 6, have a greater radial extent than adjacent regions of the respective sections 20, 22, over which they extend radially. This is to ensure that the pipette tip 10 comes into contact only radially with the guide surfaces and by the interaction of the guide surfaces with the inner wall of the coupling portion 14, the radial alignment or positioning of the pipette tip 10 is defined with respect to the coupling element 4. By the two axially offset from one another arranged guide elements 25 and 26 at the same time an oblique placement of the pipette tip 10 and tilting the same is prevented on the coupling element 4. Preferably, the two guide elements 25, 26 have an axial distance d, which is at least as large as the diameter D (radial extent) of the larger of the two guide elements, in this case the second guide member 26. Thus, the coaxial alignment of the pipette tip 10 on the coupling element 4th further improved. The distance d is here by the Distance between the respective outer edges 28, 29 of the guide elements 25, 26 defined. These outer edges form the axial end portions of the contact between the guide elements or guide surfaces 25, 26 and the pipette tip.

Corresponding to the first and second sections 20, 22 of the coupling element, the coupling section 14 of the pipette tip 10 likewise has a first section 40 and a second section 42, wherein the first section 40 has a smaller radial extent (diameter) than the second section 42. As a result, a step or shoulder 43 is formed between the first and second sections 40, 42, which serves as a sealing surface 43.

The first and second guide members 25 and 26 are formed substantially the same in the illustrated embodiment. However, it is also possible to give the guide elements each a different shape. In the present embodiment, the guide elements 25, 26 are formed circumferentially and rise with respect to the surrounding outer contour of the respective coupling element side portions 20, 22 in the form of an integrally formed ring with a circumferential guide surface whose cross-section is trapezoidal.

Between the first and second portion 20, 22 extends a radially on the outside of the coupling element 4 circumferential recess or undercut 34 in which a likewise radially encircling sealing element 21 is seated. The sealing element is conveniently a ring seal made of an elastic material. In particular, fluoroelastomers have been found to be suitable materials since they have high elasticity, longevity, high chemical resistance and low wear. In the present embodiment, the sealing element is designed as a solid, rectangular in cross-section ring. However, it is also possible to use ring seals with circular (O-rings) or X-shaped cross section. For example, ring seals with an X-shaped cross-section are more elastic than O-seals due to the individual sealing lips and therefore lead to an even better sealing of the pipette tip on the coupling element. A sealing element 21 'with an X-shaped cross-section is, for example, in FIG FIG. 4 shown. The sealing element 21 'has four sealing lips, wherein the radially outwardly to the free end 12 facing the sealing lip 23', the axial sealing portion 23, against which the corresponding sealing portion of the pipette tip is pressed.

This in FIG. 1 shown sealing element 21 has approximately the same radial extent as the second portion 22 and thereby projects beyond the first portion 20 in the radial direction. Therefore, a sealing portion 23 is axially free toward the open end 8 of the coupling element 4 substantially. The sealing portion 23 serves as an axial sealing surface and is pressed axially against the circumferentially formed inner shoulder 43 of the pipette tip 10. As related to FIG. 2 recognizable, which shows a completely attached to the coupling element 4 pipette tip 10, the sealing element 21 is only with its axial sealing portion 23 in direct contact with the inner wall of the pipette tip and in particular with the shoulder 43. This will be an axial seal and at the same time a z-orientation reached. The z-orientation is further defined by a holding element, which will be described below.

The sealing element 21 has a slightly smaller outer diameter compared to the inner diameter of the second section 42 of the pipette tip. This ensures that the inner wall of the pipette tip when sliding is not rubbed over the sealing element 21, whereby it is considerably less stressed than radial seals that must be pushed to achieve a sufficient sealing effect rubbing over usually tapered surfaces. Therefore, the maintenance of the inventive axial sealing element 21 is considerably lower.

A radial contact between coupling element 4 and pipette tip 10 is produced via the coupling element-side guide elements 25 and 26 and via first and second guide surfaces 45 and 46 of the coupling section 14 of the pipette tip 10. In the simplest case, the pipette tip-side guide surfaces 45, 46 can be formed by the inner walls of the respective sections 40, 42 of the pipette tip 10. However, it is also possible to form raised guide surfaces on the inner wall of the pipette tip. Each section of the pipette tip-side coupling section 14 has a guide surface 45, 46 which runs continuously around or consists of circumferentially distributed partial segments whose diameter corresponds to the outer diameter of the respective associated first and second guide elements 25, 26, so that a positive alignment of the pipette tip 10 is achieved.

In order to enable the most accurate alignment, the corresponding guide surfaces 45, 46 no draft angles. Entformungsschrägen are usually provided on injection molded parts in order to solve this easier of the injection mold can. By eliminating Entformungsschrägen the pipette tip-side guide surfaces extending in the axial direction parallel to the axis 6. This ensures that the radial or lateral orientation of the pipette tip does not depend on how far the pipette tip is pushed onto the coupling element. In the case of tapered guide surfaces they would be increasingly clamped when sliding the pipette tip on the coupling element on the coupling element and thereby oppose the axial movement of a resistance. Thus, conical guide surfaces affect the axial alignment and increase the required Aufschiebekraft. In Aufschiebrichtung behind the second guide member 26, an annular groove 30 for receiving an annular spring 27 is introduced. The annular spring 27 serves as a holding element and engages in an undercut 47 on the inside of the second portion 42 of the pipette tip. When placing the pipette tip this is pushed forward with its rear end 12 on the second guide member 26 and the annular spring 27 until the annular spring 27 snaps into the rear portion 47. As a result, the pipette tip is positioned axially and fixed on the coupling element. Ring spring 27 and undercut 47 make a detachable connection, which is also sufficiently stable to axially push the shoulder 43 against the axial sealing portion 23 and thus seal the pipette tip on the coupling element. The ring spring can have a slight screw thread.

When sliding the pipette tip, a reversible slight deformation of the rear end 12 of the pipette tip can occur, since the rear end is slightly stretched when passing the annular spring 27. The pipette tip should therefore be elastic at its rear end to some extent. The elasticity can be adjusted by a suitable choice of material thickness. However, it is also possible that flexible form the annular spring 27 so far that it gives in when placing the pipette tip and when passing the undercut 47 jumps into this.

The annular groove 30 is executed in the present embodiment with an inclined inner wall 31 which tapers conically to the front end 8 of the coupling element. This ensures that the annular spring 27 is axially positioned exactly towards the free end 8, since it is slightly compressed radially by the pipette tip, due to the conical inner wall 31 dodges in the direction of abutment surface 50 and pressed against this and positioned. Thus, a frictional connection results from the sealing element 21 via the Pipette-side sealing portion 43 to the undercut 47, which leads the power flow through the annular spring 27 to the stop surface 50. As a result, the pipette tip is securely attached to the coupling element and aligned.

Another embodiment shows FIG. 3 , In this embodiment, instead of an annular groove arranged in an annular spring rigid cams 57 are used as a holding element, which are distributed uniformly on the circumference of the second portion. Favorable are at least three cams. How out FIG. 3 can be seen, the cams 57 are integrally formed as a circumferential raised ring which is interrupted by cuts. With regard to the material stress of the coupling portion of the pipette tip several separate rigid cam are cheaper than a continuous ring, as this would enforce a strong expansion of the rear end 12 of the coupling portion 14 when sliding the pipette tip. Separate rigid cams, however, require only a slight deformation of the rear end 12, wherein in the case of three cams, the cross section of the second portion 42 until the engagement of the cams in the pipette tip-side undercut 47 assumes a slight triangular shape without significant material elongation. Due to the allowed cross-sectional deformation without material expansion, the force required to push the pipette tip can be significantly reduced. Alternatively, integrally formed spherical surfaces or patch studs or one or more patch rings can be used as holding means.

As in the first embodiment, the cams 57 engage in an undercut 47 at the pipette tip.

FIGS. 5 to 7 show a further embodiment. There, in turn, an annular spring (not shown) is used as a holding element, which is arranged in an annular groove 60 with parallel side walls 61, 62 and V-shaped inner wall 63. The annular groove 60 has the advantage that on the one hand the annular spring defined in the axial direction and stored on the other hand is elastically deformable in the radial direction. This facilitates the placement of the pipette tip and leads to a longevity of the annular spring.

In FIGS. 6 and 7 Details of the annular groove 60 and the first and second portions 25, 26 of the coupling element are shown. In addition, these figures show the respective guide elements, as they can be used in the other embodiments.

The V-shaped inner wall 63 (FIG. FIG. 6 ) comprises two partial surfaces which are at an obtuse angle to each other, wherein these are arranged symmetrically with respect to the axis 6. The second guide element 26 projects beyond surrounding regions of the coupling element-side second section 22. As can be seen, symmetrically formed start flanks 65, 66 are integrally formed laterally relative to the second guide element 26.

In the first section 20 ( FIG. 7 ) is formed axially to the first guide member 25 also has a rear approach flanks 67 and a front cone-shaped insertion bevel 68 for pre-centering the pipette tip. The to the free end 8 extending chamfer 68 terminates at an end face 69 on which the through hole 5 ends.

The coupling elements described above can be arranged on manual pipette holders but also on automatic pipetting machines which have many coupling elements. Such automatic pipetting machines also have further components, in particular means for stripping the pipette tips. Usually, these means comprise a relative to the coupling element in the axial direction movable scraper, which engages behind the rear end 12 of the pipette tip 10 and pushes against the Aufschiebrichtung 2 from the coupling element.

In FIG. 8 a section 42 of the pipette-side coupling section is shown enlarged. This section has a tapered inner wall 70. The cone angle (angle between Innwand 70 and longitudinal axis 6) is only a few degrees and is preferably between 0.5 ° and 1 °. This slightly conical design is a so-called Entformungsschräge to solve the injection molded part shaped pipette tip easier from the injection mold. As can be seen, the outer wall 71 of the coupling portion is also cone-shaped for this reason. In the inner wall 70, a cylindrical guide surface 72 is integrated, ie, the guide surface 72 extends in the longitudinal direction parallel to the longitudinal axis 6. Thus, a shoulder 74 between guide surface 72 and inner wall is formed, the depth of the cone angle and the longitudinal extent of the guide surface 72 depends. It is favorable if the guide surface merges directly into the conical inner wall 70 towards the far end of the cone.

FIG. 9 shows an embodiment with improved flexibility of the pipette side coupling portion 14. As can be seen, the coupling portion 14 (or the second portion of the pipette tip) has longitudinal cuts 82 which are filled with a separate material to form axial soft components. The material 82 of the axial soft components 82 is compared to the material 80, of which the main part of the coupling portion 14 is made, elastic and thereby increases the radial flexibility of the coupling portion. The incisions 82 can, as in FIG. 9 indicated, pass through the undercut 34 for receiving the coupling element-side holding element. For the production of such two-component pipette tips, an injection molding process can likewise be used. The pipette tip furthermore has a section 84 attached to the coupling section 14 and conically tapered in the axial direction, which has an opening for sucking in a medium to be pipetted at its axial end remote from the coupling section 14.

In all designs, the pipette tip may be polypropylene and filled with graphite to allow for capacitive level measurements.

The sealing element may in all embodiments consist of fluoroelastomer, e.g. Viton® or Kalrez® from DuPont. Other elastic materials are also suitable, depending on the medium to be pipetted.

The coupling elements, which are also often referred to as a mandrel, are made of a preferably corrosion-resistant metal, e.g. Stainless steel or other alloys, e.g. Tantalum, titanium or tungsten included. However, it is also possible to use the coupling elements of suitable, e.g. produce conductive plastic. Also composites of different materials are possible, e.g. Stainless steel with plastic inserts or compounds of different conductive and non-conductive plastics.

The embodiments described above have in common that they allow the placement and stripping of the pipette tip with relatively little effort. This is achieved on the one hand by the coupling element-side flexible holding elements and on the other by flexible regions of the rear end 12 of the pipette tip. In addition, all coupling elements on a low-wear or even wear-free seal, since the sealing element is designed as an axial sealing element. The Guide elements allow accurate radial or lateral (x and y direction) positioning and prevent tilting of the pipette tip. The axial positioning (z-direction) is determined on the one hand by the interaction of coupling element-side holding element with pipette tip side holding means and on the other hand by the pressing of the shoulder 43 against the sealing element 21. The seal and the attachment are thus spatially and functionally separated from each other and allow a positionally secure attachment of the pipette tip on the coupling element. Both the pipette tip and the coupling element can be produced inexpensively and are robust in use.

LIST OF REFERENCE NUMBERS

2

sliding-on

4

coupling element

5

Through opening

6

longitudinal axis

8th

free end of the coupling element

10

pipette tip

12

rear end of the pipette tip / first axial end

14

Coupling section of the pipette tip

20

first section of the coupling element

21, 21 '

sealing element

22

second section of the coupling element

23, 23 '

sealing portion

25

first guide element

26

second guide element

27

Ring spring / retaining element

28, 29

outer edge

30

ring groove

31

Inner wall of the annular groove

34

Recess / undercut

40

first section of the pipette tip

42

second section of the pipette tip

43

Sealing section / shoulder

45

first guide surface

46

second guide surface

47

undercut

50

stop surface

57

Cam / retaining element

60

ring groove

61, 62

Side walls of the annular groove 60

63

Inner wall of the annular groove 60

65, 66, 67

start flanks

68

chamfer

69

face

70

inner wall

71

outer wall

72

guide surface

74

paragraph

80

first material

82

second material

84

conical section

Claims (29)

1. Device for mounting pipette tips, having a coupling element (4) with a longitudinal axis (6) that extends in the axial direction and has a free end (8) from which a pipette tip (10) can be slid onto the coupling element (4) in the axial direction, wherein the coupling element has:

   - a sealing element (21, 21') made from a resilient material which has an axial, radially extending sealing portion (23, 23') which is exposed in the axial direction towards the free end (8) of the coupling element (4), against which a sealing portion (43) of the pipette tip (10) can be pressed axially at least in part, characterized in that

   the coupling element (4) has at least one holding element (27, 57) arranged on the outside thereof for interacting with holding means (47) of the pipette tip in order to press the sealing portion (43) of the pipette tip (10) against the axial sealing portion (23, 23') and to position the pipette tip in the axial direction, wherein the holding element is a peripheral spring element (27) which is arranged in a peripheral depression (30) located on the outside of the coupling element.
2. Device according to Claim 1, characterized in that the coupling element (4) has at least one preferably single-part or multi-part guide element (25, 26) arranged on the outside thereof for aligning the pipette tip (10) laterally.
3. Device according to Claim 2, characterized in that the coupling element has two guide elements (25, 26) set axially apart from each other on the outside of the coupling element.
4. Device according to Claim 3, characterized in that the guide elements (25, 26) each form a radially encircling guide ring having a predefined radial and preferably a constant radial extension, wherein the guide rings have a different radial extension and are of continuous and/or interrupted construction preferably independently of one another.
5. Device according to Claim 3 or 4, characterized in that the guide elements (25, 26) are at a distance (d) from each other, which distance is at least as great as the radial extension (D) of the guide elements or of the larger of the two guide elements.
6. Device according to any one of the preceding claims, characterized in that the coupling element (4) has at least one holding element (27, 57) arranged on the outside thereof for interacting with holding means (47) of the pipette tip in order to press the sealing portion (43) of the pipette tip (10) against the axial sealing portion (23, 23') and/or to position the pipette tip in the axial direction.
7. Device according to any one of the preceding claims, characterized in that the coupling element (4) has a first portion (20) which is arranged close to the free end (8) of the coupling element and a second portion (22) which is arranged with an axial offset relative to the first portion (20) in the pushing-on direction.
8. Device according to Claim 7, characterized in that the first portion (20) has a smaller radial extension than the second portion (22) preferably at each point.
9. Device according to Claim 7 or 8, characterized in that one guide element (25, 26) is arranged on each of the first and second portions (20, 22).
10. Device according to any one of Claims 7 to 9, characterized in that the sealing element (21, 21') is arranged between the first and second portions (20, 22) .
11. Device according to any one of Claims 7 to 10, characterized in that the holding element (27, 57) is arranged on the second portion (22).
12. Device according to any one of the preceding claims, characterized in that the sealing element (21, 21') consists of a fluoroelastomer.
13. Device according to any one of Claims 6 to 12, characterized in that the holding element is a peripheral spring element (27) which is arranged in a peripheral depression (30) located on the outside of the coupling element.
14. Device according to any one of Claims 6 to 12, characterized in that the holding element has one or more radial elevations (57) which are arranged in a partially or annularly encircling manner on the outside of the coupling element and are preferably rigid or flexible.
15. Device according to any one of Claims 6 to 14, characterized in that the holding element (27, 57) is arranged behind all guide elements (25, 26) when viewed in the pushing-on direction.
16. Device according to any one of the preceding claims, characterized in that the sealing element (21, 21') is elastically deformable in its material cross section.
17. Device according to any one of the preceding claims, characterized in that the coupling element (4) has an insertion bevel (68) at its free end (8) for pre-adjusting the pipette tip.
18. Use of a pipette tip for placing on the device for mounting according to any one of the preceding claims, wherein the pipette tip has

    - a longitudinal axis (6); and

    - a coupling portion (14) extending in the longitudinal axis (6) for pushing onto the mounting, wherein the coupling portion (14) has a first portion (40) and a second portion (42) offset axially with respect to the first portion (40) in the pushing-on direction (2), and the first portion (40) has a smaller radial extension than the second portion (42), and wherein at least one portion (40, 42) has an inner wall (70) at least sections of which taper conically counter to the pushing-on direction (2), in which a guide surface (45, 46, 72) that is cylindrical relative to the longitudinal axis (6) is integrated, characterized by

    - a sealing portion between the first and the second portions (40, 42) with as sealing surface (43) facing axially in the pushing-on direction (2) for interacting with the sealing element of the mounting.
19. Use according to Claim 18, characterized in that the inner wall (70) is aligned at an angle greater than 0.2° and preferably between 0.5° and 3° relative to the longitudinal axis (6) in the direction of the longitudinal axis.
20. Use according to Claim 18 or 19, characterized in that each of the first and second portions (40, 42) has conically tapering inner walls, in each of which a cylindrical guide surface (45, 46, 72) is integrated.
21. Use according to any one of Claim 18 to 20, characterized in that it has at least one holding means (47) arranged on the inner wall of the second portion (42) for interacting with a holding element of the mounting.
22. Use according to Claim 21, characterized in that the holding means (47) is an undercut.
23. Use according to any one of Claims 18 to 22, characterized in that the pipette tip is an injection moulded part.
24. Use according to any one of Claims 18 to 23, characterized in that coupling portion (14) comprises an end area which is designed to be more flexible than the other areas of the coupling portion (14).
25. Use according to any one of Claims 18 to 24, characterized in that the coupling portion (14) is made from a first material (80) and has incisions (82) extending in the longitudinal direction which are filled with a second material that is more resilient than the first material.
26. Use according to any one of Claims 18 to 25, characterized in that the sealing section is a shoulder between the first and second portions (40, 42) .
27. Pipetting device with

    (a) a coupling element (4) according to any one of Claims 1 to 17 and

    (b) a pipette tip (10) which is detachably fastenable to the coupling element (4) having a sealing portion (43) that is embodied as an axial surface facing in the direction of the coupling element (4) relative to the longitudinal axis (6) of the coupling element (4),

    and wherein in the coupled state at least a part of the sealing portion (23, 23') of the coupling element (4) is pressed axially against at least one part of the sealing portion (43) of the pipette tip (10).
28. Use according to any one of claims 18 to 26,

    - wherein the coupling element (4) has at least one guide element (25, 26) arranged on the outside thereof for aligning the pipette tip (10) laterally, and preferably has as many guide elements (25, 26) as the pipette tip (10) has guide surfaces (45, 46, 72),

    - wherein the guide element or elements (25, 26) is/are embodied independently of one another, preferably as a single part or as multiple parts

    - and wherein each guide element (25, 26) has at least partial surfaces of a cylindrical lateral surface, each of which corresponds to a cylindrical guide surface (45, 46, 72) which interacts with the partial surface on the pipette tip (10).
29. Pipetting device according to Claim 27, characterized in that the coupling element (4) has at least one holding element (27, 57) arranged on the outside thereof for interacting with at least one holding means (47) of the pipette tip (10), wherein the at least one holding element (27, 57) is designed preferably either rigidly or flexibly relative to the at least one holding means (47).

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