EP3575000A1 - Pipette tips - Google Patents

Abstract

Plastic pipette tip with an elongated tubular body with a lower opening at the lower end for the passage of liquid and an upper opening at the upper end for clamping onto a neck of a pipetting device, with a seating area for the neck next to the upper opening on the inner circumference and on the outer circumference there is at least one groove extending in the axial direction and the tubular body is designed in such a way that when the pipette tip is plugged on, it has a pushing force of at most 5 N, preferably of 3.3 N, with the seating area on a shoulder which is at least is conical in one section, the smallest diameter of this section being 3 mm and its cone angle being 2 °, being plastically stretched in the circumferential direction within the groove.

Description

The invention relates to a pipette tip.

Pipette tips are used with pipettes and other dosing devices, especially in medical, biological, biochemical and chemical laboratories for dosing liquids. Hereinafter, pipettes and other metering devices are collectively referred to as "pipetting devices". Pipette tips have an elongate, tubular body having at the lower end a lower opening for the passage of liquid and at the upper end an upper opening for clamping onto the neck of a pipetting device. Pipette tips usually have a generally conical shape whose cross-section increases from the lower opening to the upper opening. Standardized conical or frusto-conical approaches (working cone) with a standard geometry that is uniformly used by many manufacturers and characterized for each pipette tip size by a specific mean diameter and by a specific cone angle of the conical approach are known.

Multi-channel pipetting devices serve to simultaneously receive liquid from one or more vessels or to dispense into one or more vessels. They are widely used for the processing of microtiter plates, which have a multiplicity of vessels in a matrix-like arrangement. For this purpose, multichannel pipetting devices have a plurality of conical attachments arranged parallel next to one another in one or more parallel rows and onto which pipette tips can be clamped. Adapting to a commonly used format of 384 (16 x 24) (ANSI) microtiter plate microtiter plates, multi-channel pipettes of 16 or 24 batches in a row are known. Also known are multichannel dosing devices with a dosing head having 384 lugs. Corresponding the distance between adjacent vessels of microtiter plates with 384 vessels, adjacent lugs on a distance of 4.5 mm from each other.

When embodied as an air cushion pipetting device, the pipetting device has at least one displacement device for air, which is communicatively connected to a through-hole of at least one projection. An air cushion can be displaced by means of the displacement device in order to suck liquid into a pipette tip clamped onto the projection and eject it. The displacement device is usually designed as a cylinder with piston displaceable therein. But also displacement devices are known with a displacement chamber and at least one deformable wall, wherein a deformation of the wall causes the displacement of the air cushion.

In the embodiment as a direct displacer pipetting device, a small piston is arranged in the pipette tip, which is coupled when attaching the pipette tip to a projection with a coupling element of a piston drive of the pipetting device, which is displaceable in a through hole of the neck.

The inclusion of the liquid in the pipette tip is preferably carried out in a single step or in several small steps. The delivery of the liquid takes place during the pipetting in a single step and during dispensing in several small steps.

Pipetting devices usually have an ejector, which acts on the upper edge of the pipette tip to squeeze them from the approach. In multi-channel pipetting devices, the ejector can be pressed simultaneously against the upper edges of several pipette tips. The ejector allows the user to separate the liquid-contaminated pipette tips from the batch without touching them.

The pipetting device may be a handheld pipette that the user can hold and manipulate with one hand. It can also be a dosing station ("pipetting station") or an automatic dosing machine ("automatic pipetting") in which a dosing head with one or more attachments can be displaced on a robot arm or on another transmission system above a working surface. The pipetting device may also be part of a workstation which, in addition to metering, may perform further treatments of liquids (e.g., mixing, tempering, analyzing).

To avoid misdosing, the pipette tip must be clamped sufficiently tightly or sealingly on the attachment. In addition, the forces for attaching and dropping the pipette tip from the neck should not be too high. Conventional pipette tips are thick-walled and rigid in the area of contact with the conical approach. When attaching the pipette tips are widened elastically on the circumference by the approach. The spring characteristic is steep, so high Aufsteckkräfte are applied. After plugging in, a correspondingly high amount of static friction acts between the attachment and the pipette tip, which must be overcome when dropped. The user is burdened by the high forces for attaching and dropping the pipette tip. As a result, diseases can be triggered, which are summarized under the term "cummulative trauma disorders" (CTD). As far as the plugging and dropping by means of motor drives, they must be correspondingly powerful and have a high power consumption.

The US 6,197,295 describes a pipette tip that can be fixedly attached to a pipette attachment by the use of relatively low axial thrust loads of six pounds (26.7 N) and disposable therefrom by the use of relatively low three pounds (13.3 N) ejection forces. The pipette tip has a conical upper end with an inner diameter at the upper end, the greater than the diameter of the neck of the pipette onto which the pipette tip is to be placed. Further, the pipette tip has a hollow central portion and an annular sealing portion at the junction between the upper end and the central portion. The middle section has on and adjacent to the sealing area on a side wall with a wall thickness between 0.2 and 0.5 mm. The annular sealing area has an inner diameter smaller than a value "x" and is designed to engage the lower end of a seal zone of the lug to be radially expanded when the lug is inserted. As a result, a liquid-tight seal between the sealing zone of the approach and the sealing region of the pipette tip is generated. Further, the pipette tip on the inside adjacent to the sealing region has lateral stabilizing means which engage the outer surface of the neck to stabilize the pipette tip on the neck. The lateral stabilizing means have at least three circumferentially spaced contacts extending inwardly from the inner surface of the pipette tip. The diametrical spacing of the contacts is sized to easily engage the lower end of the lug and allow the lower end to slip past without widening the sidewalls of the pipette tip on which the contacts are located. As the lower end of the seal zone of the lug engages the seal area of the pipette tip, the pipette tip is stretched in the seal area and immediately adjacent thereto. As the contacts guide the pipette tip on the hub, the sidewall of the pipette tip deforms inwardly between the contacts and does not expand, thereby minimizing the force required to depress the hub. The approach can be pressed deeper into the pipette tip as the attachment force increases. Correspondingly high release forces must be applied to detach the pipette tip from the shoulder. The design is due to the inwardly projecting contacts only for relatively large pipette tips.

The US 6,568,288 describes a pipette tip having axially spaced apart annular sealing and substantially cylindrical lateral guide portions, the sealing portion being sufficiently thin to provide an interference fit and airtight seal between a pipette having axially spaced apart annular sealing and cylindrical lateral guide zones a sealing surface of the sealing zone and the sealing area to form. The wall thickness in the sealing area is preferably between 0.2 and 0.5 mm. The sealing surface is the outer surface of an annular, radially outwardly projecting projection adjacent to the lower end of the neck. The pipette tip has an annular, upwardly facing and inwardly directed shoulder on the inner periphery to limit attachment to the neck. The force for attachment should be about two pounds (8.9 N) and about one pound (4.45 N) for shedding. The depth stop may result in incomplete immersion when simultaneously picking up multiple pipette tips from a tray or rack using a multi-channel pipetting device. As the tray or rack deflects slightly down between side edges, placing the two outer tabs on the shoulders of the two outer pipette tips may result in insufficient dipping of the further tabs into the interposed pipette tips.

The US 6,967,004 B2 describes a pipette tip having an annular sealing area with an inner sealing surface on a side wall sufficiently thin in the sealing area to expand slightly and to provide an interference fit and an airtight seal between the sealing surface and a sealing zone of a pipette tip inserted into the pipette tip form. The pipette tip has an annular, inwardly and upwardly directed shoulder which limits the insertion of the neck. The approach has two cylinder sections with different diameters. Its annular sealing zone closes a sealing edge at a connection of the lower end of a Cylinder portion and the outermost edge of a radially extending transition of the neck. Preferably, the forces for inserting and dropping the pipette tip are less than two pounds (8.9 N). The depth stop may result in insufficient plunging of lugs when simultaneously receiving multiple pipette tips by means of a multi-channel pipetting device.

The EP 2 138 234 A1 describes a pipette tip having a flexible, tubular connecting portion with a wavy contour in cross-section for releasable connection to the neck of a pipetting device at the upper end of an elongated tubular portion, which increases the extensibility of the seating area. The seating area is reversibly stretchable by more than 20% when placed on the neck. For a sealing seat, the wavy contour on the approach must be smoothed, whereby the further elasticity is only slight. As a result, the pipette tip requires accurate manufacture. Furthermore, there is an inwardly radially projecting shoulder between the seating area and the tubular area which provides a depth stop for the lug which may result in insufficient immersion of lugs when receiving pipette tips by means of a multi-channel pipetting device.

The EP 2 606 977 A1 describes a pipette tip having the shape of an elongate tube with a lower opening at the lower end for the passage of liquid and an upper opening at the upper end, wherein adjacent to the upper opening on the inner periphery there is a seating area which is adapted for attachment to a standardized one conical approach of a pipetting device is used. The seating area has a holding area with radially inwardly projecting, axially extending ribs and, below the holding area, a sealing area with a peripheral, inwardly projecting sealing projection. The seating area is designed so that when plugged onto the neck with an attachment force, the holding and sealing of the pipette tip on the neck ensures the ribs are partially plastically deformed and outside of the ribs in the seating area an elastic deformation occurs. Under the sealing area, it has a comically widening to upper opening towards brake area to limit the Aufsteckens. As a result, a secure seal on the approach of a pipetting device is ensured and the ejection force applied for ejection substantially reduced. The design is particularly suitable for relatively large pipette tips with 2.5, 5.0 and 10 mL nominal volumes. For smaller pipette tips, it is less well suited due to the difficult production of filigree ribs.

The EP 3 115 110 A1 describes a pipette tip with a tubular body and a seating area for attachment to a conical neck of a pipetting device having at the inner periphery at a distance from the upper opening a circumferential, inwardly projecting sealing projection, below the sealing projection a circumferential, downwardly stronger than the Approach tapered brake area and above the sealing projection has a circumferential, inwardly projecting support projection. The sealing projection is sealingly clamped under elastic deformation on the approach, wherein the brake area is applied further down the approach and the support projection rests further up without bias on the approach or is complained of by a circumferential gap from the neck. The pipette tip is easy to seal and securely clamped on the neck of a pipetting device, can be thrown off the neck with reduced effort and is also well suited for smaller pipette tip sizes. A disadvantage is the still high effort when clamping on the approach and stripping the approach.

Based on this, the present invention seeks to provide a pipette tip that can be clamped with reduced Aufsteckkraft on a neck of a pipetting device so that it is held sufficiently tight or sealing, and which is releasable with reduced release force of the approach. The Pipette tip should be suitable for use with a multi-channel pipetting device.

The object is achieved by a pipette tip having the features of claim 1. Advantageous embodiments of the pipette tip are specified in subclaims.

The plastic pipette tip according to the invention comprises an elongated tubular body having a lower opening at the lower end for the passage of liquid and an upper opening at the upper end for clamping onto a projection of a pipetting device, wherein adjacent to the upper opening on the inner periphery of a seating area for the projection and at least one axially extending groove is present on the outer periphery and the tubular body is formed so that this when attaching the pipette tip with a Aufsteckkraft of a maximum of 5 N, preferably of 3.3 N, with the seating on a neck, which is conical at least in one section, wherein the smallest diameter of this section is 3 mm and its cone angle is 2 °, is plastically stretched within the groove in the circumferential direction.

Through the groove of the tubular body is weakened in the seating area so that it is plastically extensible by clamping on the approach of a pipetting device within the groove in the circumferential direction. This plastic deformation is based on the fact that when plugging onto the projection in the wall portion of the tubular body within the groove so high stresses occur that the elastic limit is exceeded and the plastic deformation occurs. The plastic deformation is an irreversible deformation, ie a deformation that does not regress automatically after loosening the pipette tip from the approach. In the circumferential direction next to the groove, the tubular body has a greater wall thickness than inside the groove. As a result, he will not be next to the groove plastically deformed when the plastic deformation occurs inside the groove. As a result, the attachment force can be kept low. Due to the plastic deformation within the groove, the inner diameter of the tubular body is permanently increased. The plastic deformation limits the Aufsteckkraft to values at which the pipette tip sits sufficiently tight or sealing on the approach. As a result, the Aufsteckkraft and the ejection force required to eject the pipette tip is kept low. In the case of the pipette tip according to the invention, the attachment and ejection forces for attaching a pipette tip to a projection and the ejection of the pipette tip from the projection are limited to a value of 5 N, preferably 3.3 N. The attachment force is introduced vertically into the pipette tips. The fact that the pipette tip can make do without a depth stop, a plurality of pipette tips can be accommodated by means of a multi-channel pipetting so that the approaches in all pipette tips deep enough for a safe and sealing seat dive without the Aufsteckkräfte rise sharply. According to a preferred embodiment, the pipette tip has no braking area or a braking area which, as a "gentle" depth stop, gradually slows down the approach when immersed in the pipette tip. The pipette tip is particularly suitable for use with a multichannel pipetting device having 16, 24, 384, or other number of channels. The pipette tip is particularly suitable for provision to multiple on a tray or a rack with a spacing between adjacent pipette tips of 4.5 mm for simultaneous recording by means of a multi-channel pipetting device. The pipette tip is therefore particularly suitable for the collection and delivery of liquids from or into a microtiter plate with 384 vessels.

The plastic strain in the circumferential direction may be anywhere within the groove or limited to a portion within the groove. The plastic strain in the circumferential direction within the groove is determined by the shape and dimensions of the tubular body, the shape and dimensions of the groove and the plastic Pipette tip determined. The plastic strain can be determined in particular by marking the ends of a circumferentially extending distance within the groove and measuring the distance before and after plugging the pipette tip with the predetermined maximum Aufsteckkraft on the given approach. The ends of the path can in particular be marked by the lateral edges of a line which is applied by means of a Tuschefüllers or Feinschreiber ( Fineliner ) with a defined line thickness in the axial direction within the groove. Further, it is possible to determine the plastic deformation by comparing the dimensions of the groove or the bottom of the groove in the circumferential direction before and after the attachment to the approach. The dimensions can be measured in particular by means of a microscope.

According to a further embodiment, the groove is formed so that it is plastically stretched in an axially extending strip-shaped portion having a width of at most 0.1 mm, preferably at most 0.02 mm, preferably 0.015 to 0.005 mm, preferably 0.011 mm. In this embodiment, the plastic strain can be checked by measuring the width of an applied on the strip-shaped portion by means of a Tuschefüllers or Feinschreibers line before and after attachment to the approach.

According to a further embodiment, the groove is formed such that it is plastically stretched in a section by at least 8%.

According to a further embodiment, the tubular body at the bottom of the groove has a wall thickness of at most 0.2 mm and / or in the circumferential direction next to the groove has a wall thickness of at least 0.25 mm. The bottom of the groove is that part or that portion of the groove on which the groove has the greatest depth in a horizontal cross-sectional plane through the tubular body. According to a preferred embodiment, the tubular body at the bottom of the groove has a wall thickness of at most 0.2 mm everywhere. Preferably Pipette tips made of at least one polyolefin, preferably of at least one polypropylene (PP) and / or polyethylene (PE), which comply with these wall thicknesses can be stretched plastically in the circumferential direction during insertion with the defined maximum force on the defined approach within the groove, without next to Groove plastically stretched.

According to another embodiment, the tubular body at the bottom of the groove has a wall thickness of at least 0.15 mm. This is advantageous for a sufficiently tight fit of the pipette tip on the approach. According to another embodiment, the tubular body at the bottom of the groove has a wall thickness of at least 0.15 mm everywhere.

According to a preferred embodiment, the tubular body has in the circumferential direction next to the groove everywhere a wall thickness of at least 0.25 mm. In this embodiment, the tubular body in any horizontal cross-sectional planes through the groove outside the groove everywhere has a wall thickness of at least 0.25 mm.

According to a further embodiment, the tubular body has on the inner circumference of the seating area an inwardly projecting circumferential sealing bead. The sealing bead is advantageous for the firm and sealing fit of the pipette tip on a shoulder. The sealing bead reduces the attachment and ejection forces.

According to a further embodiment, the tubular body in a horizontal cross-sectional plane through the sealing bead at the bottom of the groove has a maximum wall thickness of 0.2 mm and / or at least 0.15 mm. This is advantageous for limiting the Aufsteck- and ejection forces by plastic deformation within the groove and for a sufficiently tight fit of the pipette tip on the approach.

According to a further embodiment, in a horizontal cross-sectional plane through the tubular body, the groove has a first radius with the bottom of the groove at the lowest point. According to a further embodiment, the flanks of the groove are connected directly to the first radius. According to a further embodiment, the flanks of the groove are each connected to the outer circumference of the tubular body via a second radius.

According to a further embodiment, the first radius is at most 0.5 mm and / or at least 0.1 mm, preferably 0.25 mm.

According to a further embodiment, the groove has in the circumferential direction a maximum width of 1.5 mm and / or at least 0.25 mm, preferably 0.8 mm.

According to a further embodiment, the wall thickness of the tubular body in the circumferential direction next to the groove is at least 0.3 mm and / or at most 0.4 mm. As a result, material is saved and yet achieved an advantageous rigidity of the pipette tip.

According to a further embodiment, the sealing bead is arranged at a distance from the upper opening. As a result, the insertion of the approach is facilitated in the pipette tip. To further facilitate insertion, the pipette tip has an insertion bevel at the upper opening on the inner circumference. This has a conical contour tapering towards the sealing bead.

According to another embodiment, the distance of the sealing bead from the upper opening is at least 0.1 mm and / or at most 4.0 mm, e.g. 0.8 mm.

According to a further embodiment, the insertion bevel has a cone angle in the range of 5 to 25 °, for example 16 °.

According to a further embodiment, the tubular body has a plurality of grooves on the outer periphery. As a result, a uniform widening and limiting the Aufsteck- and ejection forces can be achieved. According to another embodiment, the grooves are distributed uniformly over the outer circumference of the tubular body. According to another embodiment, exactly three grooves are present on the outer circumference of the tubular body.

According to a further embodiment, the tubular body in the seating area is internally conical with downwardly decreasing diameter. This is advantageous for clamping on a conical approach. According to a further embodiment, the seating area has a cone angle of 1.5 to 2.5 °, preferably 2 °. The shallow cone angle is advantageous for a low-friction clamping of the pipette tip on a neck. Preferably, the approach has a cone angle exceeding the cone angle of the seating area, preferably from 1.5 ° to 3 °, more preferably 2 °.

According to a further embodiment, the tubular body on the inner periphery of the seating area below or above the sealing bead on an inwardly projecting, closed or partially circumferential guide structure. According to a further embodiment, the guide structure is a guide bead or has a plurality of guide cams distributed in the circumferential direction. The guide structure supports the pipette tip laterally at the hub so that the pipette tip does not tilt on the hub, such as when dispensing liquid under contact of the bottom of the pipette tip with a wall of the vessel ("wall delivery"). The guide structure is preferably dimensioned so that it rests without pretension on the approach or is spaced by a circumferential gap from the approach when the pipette tip is clamped onto the approach. As a result, the forces for attaching the pipette tip are kept low on the approach.

According to a further embodiment, the guide structure of the sealing bead has a distance which corresponds at least to the inner diameter of the sealing bead. This is advantageous for guiding the pipette tip at the neck.

According to a further embodiment, the sealing bead has an inner diameter of not more than 3.6 mm, preferably 3.5 mm, and / or the guide structure has an inner diameter of not more than 3.5 mm, preferably 3.4 mm.

According to a further embodiment, the tubular body at the inner periphery of the seating area below the sealing bead, preferably below the guide structure, a downwardly tapered, conical braking area. The brake area gradually slows down the approach as it enters the pipette tip. According to a preferred embodiment, the braking area is present in addition to a guide structure. Alternatively, the brake area replaces the guide structure so that it guides the pipette tip at the base. According to a further embodiment, the braking region has a cone angle of at least 5 ° and / or of a maximum of 60 °, for example of 40 °.

The groove extends in the axial direction at least over part of the height of the seating area. According to a further embodiment, the groove extends in the axial direction over the entire height of the seating area. According to another embodiment, the groove does not extend beyond the seating area in the axial direction. According to another embodiment, the groove extends in the axial direction beyond the seating area. According to another embodiment, the groove extends axially upward and / or downward beyond the seating area.

According to a further embodiment, the pipette tip has a conical starting portion, above a conical middle portion with a smaller cone angle than the initial portion and about a cylindrical head portion, wherein if necessary. Between the starting portion and the central portion, a transition portion having a larger cone angle than the initial portion is present.

According to a further embodiment, the at least one groove is arranged on the outer circumference of the head portion and / or the seat portion on the inner circumference of the head portion.

According to another embodiment, the pipette tip has a nominal volume of at most 120 μl, preferably 100 μl or 20 μl.

The pipette tip is preferably made of a single or several different plastics.

According to a further embodiment, the pipette tip is made of at least one thermoplastic, preferably of at least one polyolefin, preferably of at least one polypropylene (PP) and / or polyethylene (PE).

Preferably, the pipette tip is produced by injection molding of at least one plastic.

According to a further solution of the problem, the plastic pipette tip according to the invention comprises an elongated tubular body having a lower opening at the lower end for the passage of liquid and an upper opening at the upper end for clamping onto a projection of a pipetting device, adjacent to the upper opening on the inner circumference a seating area for the approach and on the outer circumference at least one in Axially extending groove is present and the tubular body at the bottom of the groove has a maximum wall thickness of 0.2 mm and in the circumferential direction next to the groove has a wall thickness of at least 0.25 mm.

According to one embodiment, the above pipette tip additionally has the features of one of claims 1 to 14 or one of the previously described further embodiments of this pipette tip.

Furthermore, the invention relates to a pipetting system comprising at least one pipette tip according to any of claims 1-14 or any of the preceding further embodiments and a single-channel pipetting device with a single attachment for attaching a pipette tip and / or a multi-channel pipetting device with multiple approaches for simultaneous attachment multiple pipette tips, wherein the multi-channel pipetting device preferably has a dosing with 16 or 24 or 384 approaches.

According to a further embodiment, the at least one projection has at least one conical section, wherein the smallest diameter of this section is 2.5 to 3 mm, preferably 3 mm, and its cone angle is 1.5 to 3 °, preferably 2 °.

Fig. 1a-d

eine Pipettenspitze mit 20 µl Nennvolumen in Seitenansicht (Fig. 1a), in einem Längsschnitt (Fig.1b), in einer vergrößerten Draufsicht (Fig. 1c) und in einer Perspektivansicht von der Seite (Fig. 1d);

Fig. 2a-d

eine Pipettenspitze mit 100 µl Nennvolumen in einer Seitenansicht (Fig. 2a), in einem Längsschnitt (Fig. 2b), in einer Draufsicht (Fig. 2c) und in einer Perspektivansicht von der Seite (Fig. 2d);

Fig. 3

einen Ansatz zum Aufstecken der Pipettenspitze in einer Seitenansicht;

Fig. 4a-d

die Pipettenspitze mit einem Nennvolumen von 20 µl aufgesteckt auf den Ansatz in einem teilweisen Längsschnitt (Fig. 4a), in einem vergrößerten Detail b (Fig. 4b), in einem vergrößerten Teil c (Fig. 4c) und in einem Horizontalschnitt durch den Dichtbereich (Fig. 4 d);

Fig. 5a +

b eine Pipettenspitze vor dem Aufstecken auf den Ansatz (Fig. 5a) und nach plastischer Verformung innerhalb einer Nut (Fig. 5b), jeweils in einem Horizontalschnitt;

Fig. 6a-c

die Pipettenspitze mit einem Nennvolumen von 20 µl auf einer Prüfvorrichtung zum Überprüfen der plastischen Verformung in einer Seitenansicht (Fig. 6a), in ein Vertikalschnitt (Fig. 6b) und in einer Perspektivansicht schräg von der Seite (Fig. 6c);

Fig. 7a+ b

Visualisierung der Ergebnisse einer FEM-Verformungsberechnung einer erfindungsgemäßen Pipettenspitze mit Newton am Außenumfang (Fig. 7a) und einer herkömmlichen Pipettenspitze ohne Nuten am Außenumfang (Fig. 7b), jeweils in einer Perspektivansicht schräg von oben und auf die Seite der Pipettenspitze.

The invention will be explained in more detail with reference to the accompanying drawings of two embodiments. In the drawings show:

Fig. 1a-d

a pipette tip with 20 μl nominal volume in side view ( Fig. 1a ), in a longitudinal section ( 1b shows ), in an enlarged plan view ( Fig. 1c ) and in a perspective view from the side ( Fig. 1d );

Fig. 2a-d

a pipette tip with 100 μl nominal volume in a side view ( Fig. 2a ), in a longitudinal section ( Fig. 2b ), in a plan view ( Fig. 2c ) and in a perspective view from the side ( Fig. 2d );

Fig. 3

an approach for attaching the pipette tip in a side view;

Fig. 4a-d

the pipette tip with a nominal volume of 20 μl attached to the projection in a partial longitudinal section ( Fig. 4a ), in an enlarged detail b ( Fig. 4b ), in an enlarged part c ( Fig. 4c ) and in a horizontal section through the sealing area ( Fig. 4 d) ;

Fig. 5a +

b a pipette tip before attaching to the neck ( Fig. 5a ) and after plastic deformation within a groove ( Fig. 5b ), each in a horizontal section;

Fig. 6a-c

the pipette tip with a nominal volume of 20 μl on a test device for checking the plastic deformation in a side view ( Fig. 6a ), in a vertical section ( Fig. 6b ) and in a perspective view obliquely from the side ( Fig. 6c );

Fig. 7a + b

Visualization of the results of an FEM deformation calculation of a pipette tip according to the invention with Newton on the outer circumference ( Fig. 7a ) and a conventional pipette tip without grooves on the outer circumference ( Fig. 7b ), each in a perspective view obliquely from above and on the side of the pipette tip.

In the present application, the terms "vertical" and "horizontal", "top" and "bottom" and derived therefrom such as "above" and "below" on an arrangement of the pipette tip with vertically aligned central axis of the tubular body, wherein the upper opening is at the top and the lower opening is at the bottom.

According to Fig. 1-2 For example, a pipette tip 1 has an elongate, tubular body 2 which has a lower opening 4 at the lower end 3 and an upper opening 6 at the upper end 5. The lower opening 4 is smaller than the upper opening 6.

Generally, the inner and outer diameter of the tubular body 2 increases from the lower opening 4 toward the upper opening 6. The tubular body 2 has at the bottom a conical starting portion 7, above a central portion 8 with a smaller cone angle than the initial portion 7 and above a cylindrical head portion 9 with larger outer dimensions than the central portion 8. Adjacent to the central portion 8 runs on the underside of the head portion 9 outside a downwardly directed outer shoulder around.

According to Fig. 1 In the case of the pipette tip 1, the conical starting section 7 is connected to the central section 8 via a more conical transition section 10. According to Fig. 2 In the case of the pipette tip 1, the relatively short conical starting section 7 is connected directly to the relatively long central section 8. The wall thickness of the beginning section 7 and - only at the pipette tip of Fig. 1 - The transition section 10 increases slightly from bottom to top.

At the outer periphery of the head portion extending grooves 11 are provided in the axial direction. The grooves 11 extend over the entire length of the head portion 9. They are aligned parallel to the central axis of the tubular body 2. Each pipette tip 1 has three grooves 11, which are distributed uniformly over the outer circumference of the head portion 9.

Each groove 11 has a rounded profile in cross-section. At the bottom, the groove 11 has a first radius 12 with the center outside the tubular body 2. The first radius 12 smoothly merges on both sides into a second radius 13, 14 with the center point within the tubular body 2. Every second radius 13,14 goes smooth outside into the cylindrical outer contour of the head portion 9.

In addition to the upper opening 6, the tubular body 2 has a seating area 15 for a conical projection of a pipetting device. The seating area 15 extends into the head portion 9 and is conical with a cone angle of 2 °. The tubular body 2 has on the inner periphery of the seat portion 15 on an inwardly projecting, circumferential sealing bead 16. The sealing bead 16 forms the upper end of the seating area 15. An insertion bevel 17 with a conical contour extends from the upper opening 6 to the sealing bead 16. The cone angle of the insertion bevel 17 is 16 °.

The distance of the sealing bead 16 from the upper opening is 0.8 mm. The sealing bead 16 projects 0.05 mm from the seating area 15.

At a further distance from the upper opening 6, the tubular body has an inwardly projecting, closed circumferential guide structure 18 in the form of a guide bead. The guide structure 18 has a distance of 5.3 mm from the upper opening 6. The guide bead 18 protrudes 0.03 mm from the seating area 15. Alternatively, instead of the encircling guide structure 18, pointwise or partially circumferential guide structures are present, for example three guide cams distributed uniformly over the inner circumference of the seat region 15.

Below the guide structure 18, a conical braking region 19 is provided on the inner circumference of the head section 9. The cone angle of the braking area 19 is 40 °.

Below the brake area 19 is located in the head portion 9, a cylindrical cavity 20. The cavity 20 can basically remain free. In the embodiment as a filter pipette tip, one or more filter disks are pressed or held in another manner in the cavity 20.

At the lower end of the cylindrical cavity 20 there is an inwardly projecting, upwardly directed and circumferential inner shoulder 21. The inner shoulder 21 merges into the middle section 8 via a rounded contour.

At the bottom of the grooves 11 of the tubular body in a horizontal plane through the sealing bead 16 has a wall thickness of at most 0.2 mm and in the same plane next to the grooves 11 has a greater wall thickness of at least 0.25 mm. In the example, the wall thickness at the bottom of the grooves is 0.2 mm and next to the grooves 0.4 mm.

The pipette tips 1 are preferably made of polypropylene.

According to Fig. 3 has a projection 22 a rounded insertion portion 23 with a circumferential radius 24 and a maximum diameter of 3.4 mm, adjacent thereto a guide portion 25 with a small cone angle of 2 ° and a maximum diameter of 3.6 mm, adjacent thereto a clamping portion 26th with the same cone angle and a maximum diameter of 3.8 mm and adjacent thereto a cylindrical support portion 27. The approach is preferably made of stainless steel or high strength and rigid plastic, such as a thermoset.

The projection 22 is through the upper opening 6 in the pipette tip 1 to the in Fig. 4 shown position insertable. In this position, the insertion section 23 is pushed against the braking portion 19, the guide bead 18 is located on the guide portion 25 and the sealing bead 16 on the clamping portion 26 at. As a result, the inner diameter is widened in the seating area 15. The expansion is based on a plastic deformation of the wall of the pipette tip 1 within at least one groove 11. An additional elastic deformation is possible.

According to Fig. 5 is plastic deformation by an original 0.011 mm wide strip at the bottom of the groove 11 plastically expanded to a width of 0.013 mm. Between the turning points of the groove profile on the groove flanks, the groove 11 is widened plastically from 0.389 mm to 0.402 mm.

It has been observed that the plastic deformation is usually limited to one of the three grooves 11. Obviously, this is due to the fact that during injection molding of the pipette tip 1, the core of the injection molding tool is slightly displaced out of the center of the cavity, so that the wall thickness in the region of the grooves 11 is slightly different. The displacement from the center seems to be based on the back pressure of the plastic mass flowing laterally into the cavity.

Due to the plastic deformation when clamping the pipette tip 1 on the projection 22, the clamping force is limited to a sufficient for the sealing and a tight fit of the pipette tip 1 on the neck 22 value.

The plant of the guide bead 18 on the guide portion 25 prevents lateral deflection of the pipette tip 1 and thus relaxation of their seat on the neck 22, especially at Wandabgabe.

The braking area 19 gently slows down the sliding of the pipette tip 1 onto the projection 22, whereby a sufficiently firm and sealing seat of all pipette tips on all approaches is promoted when simultaneously receiving a plurality of pipette tips from a tray or rack by means of a multichannel pipetting device.

According to Fig. 6 is pressed for checking the plastic deformation of the pipette tip 1 PP of a defined Aufklemmkraft on a neck 22 made of stainless steel with a polished surface. The attachment force is limited by a coil spring 28, via which the projection 22 is supported on an abutment 29. The pipette tip 1 has plastically deformed at the bottom of a groove 11. This can be determined by marking a strip at the bottom of the groove and measuring the strip width before and after attaching the pipette tip to the projection 22.

In addition, in this arrangement, the tightness can be checked. For this, the pipette tip 1 is hermetically sealed at its lower opening 4 and applied to its upper opening 6, a vacuum.

Fig. 7a and b show the deformations of a pipette tip 1 according to the invention and a conventional pipette tip 1 with constant wall thickness in the circumferential direction when introducing a defined radial force into the seating area 15 according to FEM calculations. The amount of deformation is indicated by colors, with the values of the deformation associated with the colors in the legend. The contours of the deformed pipette tips 1 are graphically oversubscribed in color. Additional lines indicate the contours of the undeformed pipette tips 1.

The strongest deformations by the push-on forces acting radially on the seat regions 15 occur in the vicinity of the upper openings 6 of the pipette tips 1. In the case of the pipette tip 1 according to the invention, they are concentrated on the grooves 11. Since it is a calculation, all grooves 11 are equally affected. In the case of the pipette tip 1 according to the invention, the deformations on the grooves are 6.5 times as high as in the case of the conventional pipette tip 1. The deformations within the grooves 11 have plastic and elastic components. Incidentally, the deformations are elastic.

LIST OF REFERENCE NUMBERS

1

pipette tip

2

tubular body

3

lower end

4

lower opening

5

top end

6

upper opening

7

initial section

8th

midsection

9

header

10

Transition section

11

groove

12

first radius

13, 14

second radius

15

sitting area

16

sealing bead

17

chamfer

18

management structure

19

conical braking area

20

cylindrical cavity

21

inner shoulder

22

approach

23

insertion

24

circumferential radius

25

guide section

26

clamping section

27

cylindrical support area

28

coil spring

29

abutment

30

Plug

Claims (15)

Plastic pipette tip having an elongated tubular body (2) with a lower opening (4) at the lower end (3) for the passage of liquid and an upper opening (6) at the upper end (5) for clamping onto a projection (3) 22) of a pipetting device, wherein adjacent to the upper opening (6) on the inner circumference a seating area (15) for the projection (22) and at least one axially extending groove (11) is provided on the outer periphery and the tubular body is formed so that this when attaching the pipette tip with a Aufsteckkraft of a maximum of 5 N, preferably 3.3 N, with the seating area on a neck which is conical at least in one section, the smallest diameter of this section is 3 mm and its cone angle 2 ° , is plastically stretched within the groove (11) in the circumferential direction. A pipette tip according to claim 1, wherein the tubular body (2) at the bottom of the groove (11) has a maximum wall thickness of 0.2 mm and / or at least 0.15 mm and / or in the circumferential direction of the tubular body (2) in addition to the groove (11) has a wall thickness of at least 0.25 mm. A pipette tip according to claim 1 or 2, wherein the tubular body (2) has an inwardly projecting circumferential sealing bead (16) on the inner periphery of the seating portion (15). A pipette tip according to claim 3, wherein the sealing bead (16) is spaced from the upper opening (6). A pipette tip according to any one of claims 1 to 4, wherein the tubular body (2) has an insertion slope (17) on the inner periphery at the upper opening (6). A pipette tip according to any one of claims 1 to 5, wherein the tubular body (2) has a plurality, preferably three, grooves (11) on its outer periphery. A pipette tip according to claim 6, wherein the grooves (11) are evenly distributed over the outer circumference of the tubular body (2). A pipette tip according to any one of claims 3 to 7, which has an inwardly projecting, closed or partially circumferential guide structure (18) below the sealing bead (16). Pipette tip according to claim 8, wherein the guide structure (18) from the sealing bead (16) has a distance which corresponds at least to the inner diameter of the sealing bead (16). A pipette tip according to any one of claims 1 to 9, wherein the tubular body (2) has a downwardly tapered, conical braking region (19) at the inner circumference of the seating area (15) below the sealing bead (16), preferably below the guiding structure (18) ) having. A pipette tip according to any one of claims 1 to 10, having a conical starting portion (7), a conical central portion (8) at a smaller cone angle than the initial portion (7) and above a cylindrical head portion (9), optionally between the initial portion (7). 7) and the central portion (8) a transition portion (10) having a larger cone angle than the initial portion (7) is present. The pipette tip of claim 11, wherein the at least one groove (11) is disposed on the outer circumference of the head portion (9) and wherein the seat portion (15) is disposed on the inner circumference of the head portion (9). Pipette tip according to one of claims 1 to 12, which is made of at least one thermoplastic, preferably of at least one polyolefin, preferably of at least one polypropylene and / or polyethylene. A pipette tip according to any one of claims 1 to 13, having one or more of the following features: The base of the groove (11) has a first radius and the flanks of the groove (11) are directly connected to the first radius, The first radius is at most 0.5 mm and / or at least 0.1 mm, preferably 0.25 mm, The groove (11) has in the circumferential direction a maximum width of 1.5 mm, and / or at least 0.25 mm, preferably 0.8 mm, The wall thickness of the tubular body (2) in the circumferential direction next to the groove (11) is at least 0.3 mm and / or at most 0.4 mm, The distance of the sealing bead (16) from the upper opening (6) is at least 0.1 and / or at most 4.0 mm, The insertion bevel (17) has a cone angle in the range of 5 to 25 °, The seating area (15) is internally conical with the diameter decreasing downwards, the cone angle preferably being 1.5 to 2.5 °, preferably 2 °, • The sealing bead (16) has an inner diameter of at most 3.54 mm, preferably of 3.52 mm, and / or the guide structure (18) has an inner diameter of at most 3.42 mm, preferably 3.4 mm. A pipetting system comprising at least one pipette tip according to one of claims 1 to 14 and a single-channel pipetting device with a single attachment for attaching a pipette tip and / or a multi-channel pipetting device with several approaches for simultaneously attaching a plurality of pipette tips.

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