EP3939702A1 - Pipette for use with a pipette tip with integrated piston - Google Patents

Abstract

Pipette for use with a pipette tip with an integrated tip plunger, comprising: • a rod-shaped pipette housing, • a pin at the lower end of the pipette housing for holding a pipette tip, • a lifting rod for moving the tip plunger in the pipette tip, the lifting rod having a receptacle for the pipette tip at its lower end inserting the upper end of the tip plunger of a pipette tip held on the spigot and engaging with the tip plunger in a through bore of the spigot, or the lower end of the lifting rod into a receptacle at the upper end of the tip plunger of a pipette tip held on the spigot and with the tip plunger in a through hole of the spigot engaging pipette tip can be used,• the lifting rod at the lower end having first means for positively connecting the lifting rod to the tip piston and the upper end of the lifting rod having second means for positively connecting the tip piston to the first means st, so that the tip piston can be inserted into the receptacle of the lifting rod with elastic widening of the lower end of the lifting rod before the positive connection with the lifting rod, or the lifting rod can be inserted into the receptacle of the lifting rod with elastic widening of the upper end of the tip piston before the positive connection with the tip piston tip piston can be inserted,• a drive device for displacing the lifting rod for sucking a liquid sample into a pipette tip held on the spigot and ejecting the sample from the pipette tip by means of a tip piston positively connected to the lifting rod,• at least one locking sleeve arranged coaxially to the lifting rod, which in Is guided displaceably in the direction of the lifting rod in the pipette housing,• wherein the at least one locking sleeve can be moved into a locking position in which it has a lower end of the lifting rod that can be expanded by inserting the upper end of a pointed piston into the receptacle of the lifting rod, or ei ne by inserting the lower end of the lifting rod into a receptacle of the tip piston expandable upper end of the tip piston limited on the outside, whereby the locking sleeve prevents detachment of a positively connected to the lifting rod tip piston from the lifting rod, and the locking sleeve from the locked position can be moved upwards, so that the lifting rod or the upper end of the tip piston is at least partially released and the tip piston is detachable from the lifting rod.

Description

The invention relates to a pipette for use with a pipette tip with an integrated piston.

Pipettes are used in particular in scientific and industrial laboratories with medical, molecular biological and pharmaceutical fields of application for dosing selected volumes of liquids. The liquids can in particular be homogeneous (single-phase) liquids consisting of a single liquid component or of a homogeneous mixture of a plurality of liquid components (solutions). Furthermore, the liquids can be heterogeneous (multi-phase) mixtures of a liquid with another liquid (emulsions) or a solid (suspensions).

Pipettes have a stem-shaped pipette housing with a spigot (lug) at the lower end for clamping on a pipette tip. The pin is often a conical, cylindrical or partially conical and cylindrical projection and is also referred to as a "working cone". A pipette tip is a hollow tube with a tip opening at the bottom and an attachment opening at the top, with which the pipette tip can be clamped onto the spigot. The liquid is aspirated into and dispensed from the pipette tip. The uptake and delivery of the liquid is controlled by the pipette. Fixed-volume pipettes are used for pipetting constant volumes. With variable pipettes, the volume to be dosed can be adjusted. A mechanical counter is used to display the set volume. To adjust the volume, the stroke of a drive device can be adjusted by means of an adjustment device that is coupled to the counter. The pipette tip is detached from the attachment after use and can be exchanged for a fresh pipette tip. In this way, cross-contamination can be avoided during subsequent pipetting.

Air-cushion pipettes have a piston-cylinder system in the pipette housing, which is connected via a channel to a through-hole in the spigot. Pipette tips for air cushion pipettes (air cushion pipette tips) do not have an integrated piston. By displacing the piston by means of the drive device in the cylinder, an air cushion is moved in order to suck liquid into and eject liquid from a pipette tip clamped onto the spigot. A disadvantage of air cushion pipettes are dosing errors due to the change in the length of the air cushion due to the weight of the liquid sucked in and the influence of temperature, air pressure and humidity. Contamination of the pipette by aerosols can also be problematic.

Positive displacement pipettes are used with pipette tips with an integrated piston (positive displacement pipette tips). Pipette tips with an integrated plunger have a tip plunger that is inserted into the pipette tip and can be pulled further out of the pipette tip to aspirate liquid and pushed deeper into the pipette tip to dispense liquid. Positive displacement pipettes have a spigot for attaching the pipette tip and a drive device that can be coupled to the integrated piston (tip piston) for moving the piston. The piston comes in direct contact with the liquid, eliminating the effects of an air pocket. Positive displacement pipettes are particularly suitable for dispensing liquids with a high vapor pressure, high viscosity or high density and for applications in molecular biology where freedom from aerosols is important to avoid contamination.

Disposable or reusable air cushion or positive displacement pipette tips are made of plastic or glass.

In the direct displacement Biomaster ^® 4830 Eppendorf AG said drive means has a lifting rod for moving a piston in a pipette tip which has a hollow lower lifting rod part and an upper lifting rod part inserted from above into the lower lifting rod part. The upper lifting rod part is connected to a control element which protrudes from the upper end of the pipette housing. A pipette tip Mastertip ^® Eppendorf AG is clamped onto a pin of the pipette. By pressing the operating element, the lifting rod can be moved downwards, so that an upper end of the piston rod of a tip piston of the pipette tip is pressed into the lower lifting rod part. When moving the lifting rod down to a lower stop, a spring device is preloaded. After the operating element has been relieved, the spring device moves the lifting rod up to an upper stop, taking the tip piston with it and allowing liquid to be sucked into the pipette tip. The liquid sucked in can be dispensed by pressing the operating element again down to the bottom stop. To release the pipette tip, the user has to press the operating element with increased force so that another spring device compresses, the upper part of the lifting rod is shifted down in the lower part of the lifting rod, the piston is pushed out of the lower part of the lifting rod and the pipette tip is pushed off the spigot.

In order to release the pipette tip from the pipette, the spring action of the spring devices must be overcome. This can be tiring for the user, especially when the pipette tips have to be changed frequently. Furthermore, when dispensing highly viscous liquids and when dispensing liquids quickly from the pipette tip, it can happen that the pipette tip is detached from the spigot due to the increased flow resistance in the tip opening.

the DE 27 11 124 C2 describes a pipette for use with a pipette tip with an integrated piston, which can be connected to a pipette tip via a bayonet lock. The piston has a piston rod which is connected by a chuck of the pipette is held. In the closed position, the collet is pressed together by a tubular guide ring of the pipette so that it clamps around the piston rod. When the guide ring is moved upwards relative to the collet, the elasticity of the three-finger collet opens and releases the piston rod, allowing it to fall out loosely. The frictional connection between the piston rod and the collet can become loose unintentionally. In addition, the bayonet lock must be operated by hand and this can lead to contamination.

the U.S. 4,474,071 describes another pipette for use with a pipette tip with an integrated plunger, which has a spigot for attaching the pipette tip and a collet with elastically resilient fingers and a sleeve that can be slid onto the fingers for clamping the upper end of a plunger. With this pipette, too, the frictionally fastened piston can come loose unintentionally. In addition, the connection between the pipette and the plunger can require a great deal of force.

According to U.S. 2016/0271602 A1 a helical spring is arranged between the fingers in order to elastically resiliently push them apart.

Proceeding from this, the object of the invention is to provide a pipette for use with a pipette tip with an integrated plunger, in which the forces for connecting the pipette to the tip plunger and for detaching the tip plunger from the pipette are reduced and the The tip piston is held sufficiently firmly on the pipette so that it does not detach from the pipette or move in its holder when pipetting highly viscous liquids or during rapid pipetting.

• ein stangenförmiges Pipettengehäuse,
• einen Zapfen am unteren Ende des Pipettengehäuses zum Halten einer Pipettenspitze,
• eine Hubstange zum Verlagern des Spitzenkolbens in der Pipettenspitze, wobei die Hubstange an ihrem unteren Ende eine Aufnahme zum Einsetzen des oberen Endes des Spitzenkolbens einer auf dem Zapfen gehaltenen und mit dem Spitzenkolben in eine Durchgangsbohrung des Zapfens eingreifenden Pipettenspitze hat, oder die Hubstange mit ihrem unteren Ende in eine Aufnahme am oberen Ende des Spitzenkolbens einer auf dem Zapfen gehaltenen und mit dem Spitzenkolben in eine Durchgangsbohrung des Zapfens eingreifenden Pipettenspitze einsetzbar ist,
• wobei die Hubstange am unteren Ende erste Mittel zum formschlüssigen Verbinden mit dem Spitzenkolben und der Spitzenkolben am oberen Ende zweite Mittel zum formschlüssigen Verbinden des Spitzenkolbens mit den ersten Mitteln aufweist, sodass der Spitzenkolben unter elastischer Aufweitung des unteren Endes der Hubstange vor der formschlüssigen Verbindung mit der Hubstange in die Aufnahme der Hubstange einführbar ist, oder die Hubstange unter elastischer Aufweitung des oberen Endes des Spitzenkolbens vor der formschlüssigen Verbindung mit dem Spitzenkolben in die Aufnahme des Spitzenkolbens einführbar ist,
• eine Antriebseinrichtung zum Verlagern der Hubstange zum Einsaugen einer flüssigen Probe in eine auf dem Zapfen gehaltene Pipettenspitze und zum Ausstoßen der Probe aus der Pipettenspitze mittels eines formschlüssig mit der Hubstange verbundenen Spitzenkolbens,
• mindestens eine koaxial zur Hubstange angeordnete Sperrhülse, die in Richtung der Hubstange im Pipettengehäuse verlagerbar geführt ist,
• wobei die mindestens eine Sperrhülse in eine Sperrstellung verlagerbar ist, in der sie ein durch Einführen des oberen Endes eines Spitzenkolbens in die Aufnahme der Hubstange aufweitbares unteres Ende der Hubstange oder eine durch Einführen des unteren Endes der Hubstange in eine Aufnahme des Spitzenkolbens aufweitbares oberes Ende des Spitzenkolbens außen begrenzt, wodurch die Sperrhülse ein Ablösen eines formschlüssig mit der Hubstange verbundenen Spitzenkolbens von der Hubstange verhindert, und die Sperrhülse aus der Sperrstellung nach oben verlagerbar ist, sodass die Hubstange oder das obere Ende des Spitzenkolbens zumindest teilweise freigegeben wird und der Spitzenkolben von der Hubstange ablösbar ist.

The pipette according to the invention for use with a pipette tip comprises:

• a rod-shaped pipette housing,
• a spigot at the lower end of the pipette body for holding a pipette tip,
• a lifting rod for moving the tip plunger in the pipette tip, the lifting rod having at its lower end a receptacle for inserting the upper end of the tip plunger of a pipette tip held on the spigot and engaging with the tip plunger in a through hole of the spigot, or the lifting rod with its lower end end can be inserted into a receptacle at the upper end of the tip plunger of a pipette tip held on the spigot and engaging with the tip plunger in a through bore of the spigot,
• wherein the lifting rod has first means for positively connecting to the tip piston at the lower end and the tip piston has second means for positively connecting the tip piston to the first means at the upper end, so that the tip piston elastically expands the lower end of the lifting rod before the positive connection with the lifting rod can be inserted into the receptacle of the lifting rod, or the lifting rod can be inserted into the receptacle of the tip piston with elastic expansion of the upper end of the tip piston before the form-fitting connection with the tip piston,
• a drive device for displacing the lifting rod for aspirating a liquid sample into a pipette tip held on the spigot and for ejecting the sample from the pipette tip by means of a tip piston positively connected to the lifting rod,
• at least one locking sleeve arranged coaxially to the lifting rod, which is guided displaceably in the direction of the lifting rod in the pipette housing,
• wherein the at least one locking sleeve can be moved into a locking position in which it has a lower end of the lifting rod that can be expanded by inserting the upper end of a pointed piston into the receptacle of the lifting rod, or an upper end of the lifting rod that can be expanded by inserting the lower end of the lifting rod into a receptacle of the pointed piston the tip piston is limited on the outside, whereby the locking sleeve prevents a tip piston which is positively connected to the lifting rod from detaching from the lifting rod, and the locking sleeve can be displaced upwards out of the locking position, so that the lifting rod or the upper end of the tip piston is at least partially released and the tip piston is released from the Lifting rod is detachable.

In the pipette according to the invention, the first means for positively connecting the lifting rod and the second means for positively connecting the tip piston are designed to be complementary to one another, so that they form a positive connection with one another when the pipette tip is held on the spigot. Connecting the tip piston to the lifting rod is facilitated by the fact that the lifting rod can be elastically expanded by the insertion of the upper end of the tip piston or the tip piston can be elastically expanded by the penetration of the lower end of the lifting rod. The elastic expansion is caused by the forces acting between the first and second means for positive connection when telescoping the lower end of the lifting rod and the upper end of the tip piston. The elastic widening is reversed in whole or in part when, when telescoping, the second means for positively connecting the tip piston form the positively connected connection with the first means for positively connecting the lifting rod. Thereafter, the at least one locking sleeve is shifted into the locking position. This secures the tip plunger to the lift rod since the locking sleeve in the locked position prevents the lower end of the lift rod or the upper end of the plunger rod from being elastically expanded, resulting in the disengagement of the positive connection between the lifting rod and the piston rod is required. To eject the pipette tip from the pipette, the locking sleeve is removed from the locked position so that it at least partially releases the lower end of the lifting rod or the upper end of the piston rod and the lower end of the lifting rod or the upper end of the piston rod can be elastically expanded. As a result, the form-fitting connection can be released with little effort and the piston rod can be released from the lifting rod.

According to one embodiment of the invention, the lifting rod has at least one slot running in the longitudinal direction at the lower end and the locking sleeve delimits the lifting rod in the locking position, or the locking sleeve is designed to have at least one slot running in the longitudinal direction at the upper end and is positively connected to the lifting rod To limit the tip piston in the blocking position in the area of the slot on the outside. According to the first variant, the lifting rod has at least one slot running in the longitudinal direction for the elastic widening. In this case, the lifting rod can consist of a hard-elastic or soft-elastic material, for example a metal or a plastic. A lifting rod made of a flexible material, for example silicone rubber, a thermoplastic elastomer or rubber, can have sufficient elasticity for the elastic widening even without a slot. According to the second variant, the tip piston has at least one slot running in the longitudinal direction at the upper end for the elastic widening. In this case, the tip piston can consist of a hard-elastic plastic, for example polypropylene or polyethylene, or of a soft-elastic plastic. It is also possible to produce a tip piston, at least at the upper end, from a flexible material, for example silicone rubber, a thermoplastic elastomer or rubber, so that it has sufficient elasticity for elastic expansion even without a slit. The tip piston can be produced from several materials by multi-component injection molding. Here they can different materials are positively and / or chemically connected to each other. The locking sleeve is designed not to deform when loaded with a radial force sufficient to elastically expand the lift rod or the top of the tip piston. The locking sleeve consists, for example, of metal or of a hard-elastic or rigid plastic.

According to a further embodiment, the locking sleeve is connected to a first operating element which protrudes from the pipette housing and can be displaced relative to the pipette housing in order to move the locking sleeve downward into the locking position and upward out of the locking position by actuating the first operating element. The shifting of the blocking element into the blocking position and out of the blocking position upwards is simplified for the user by the first operating element. In another embodiment, which is structurally simpler, the locking sleeve is not connected to a first operating element, but can be moved by hand.

According to a further embodiment, the pipette has an ejection device, which comprises an ejection rod, which is guided in a displaceable manner in the longitudinal direction of the spigot within an axial bore of the lifting rod and is arranged with its lower end above the tip piston when this is positively connected to the lifting rod, and which comprises a second operating element connected to the ejection rod in order to displace the ejection rod, the ejection device being designed to push the tip piston off the lifting rod by displacing the ejection rod downwards and to push off the pipette tip, which includes the tip piston, from the spigot when the locking sleeve reaches the lower end at least partially releases the lifting rod or the upper end of the tip piston. This makes it easier for the user to eject the pipette tip and avoids contamination, in particular because the user does not have to touch the pipette tip to detach it from the pipette. In a structurally simple embodiment that does not have an ejection device, the user can detach the pipette tip from the pipette by hand.

According to a further embodiment, the spigot has first means for form-fitting connection with a pipette tip, so that a pipette tip, which has second means for form-fitting connection of the pipette tip with the first means for form-fitting connection of the spigot, with elastic narrowing of the spigot and/or with elastic expansion of the pipette tip can be slid onto the spigot before it is positively connected to the spigot, at least one locking sleeve is arranged coaxially with the spigot and is guided in the pipette housing so that it can be displaced in the direction of the spigot, with the at least one locking sleeve being displaceable into a locking position in which it passes a Sliding a pipette tip on the inside and/or on the outside of a pipette tip that can be widened by pushing it onto the spigot, whereby the locking sleeve prevents a pipette tip that is positively connected to the spigot from becoming detached from the spigot, and the locking sleeve can be displaced upwards from the locked position, so that the spigot and/or the pipette tip is at least partially released and the pipette tip can be detached from the spigot. In this embodiment, the first means for positively connecting the spigot and the second means for positively connecting the pipette tip are designed to be complementary to one another, so that they form a positive connection with one another when the pipette tip assumes a specific position on the spigot. The connection of the pipette tip to the spigot is made easier in that the spigot can be elastically narrowed by sliding the pipette tip on and/or the pipette tip can be elastically widened by the penetration of the spigot. The elastic narrowing and/or widening is brought about by the forces acting between the first and second means for positive connection when the pipette tip is pushed onto the spigot. The elastic narrowing and/or elastic widening is reversed in whole or in part if the second means for positively locking connection of the pipette tip enter into the positively locking connection with the first means for positively locking connection of the spigot when it is pushed on. After that, the at least one Locking sleeve shifted to the locked position. This secures the pipette tip on the spigot, since the locking sleeve in the locked position prevents the spigot from being elastically narrowed and/or the pipette tip from being elastically widened, which is necessary to release the positive connection between the spigot and the pipette tip. To eject the pipette tip from the pipette, the locking sleeve is removed from the locked position so that it at least partially releases the spigot and/or the pipette tip and the spigot can be narrowed elastically and/or the pipette tip can be widened elastically. As a result, the form-fitting connection can be broken with little effort and the pipette tip can be detached from the spigot.

According to one embodiment, the peg has at least one slot running in the longitudinal direction and the locking sleeve limits the peg on the inside in the locking position and/or the locking sleeve is designed with a pipette tip that has at least one slit running in the longitudinal direction at the upper end and is positively connected to the peg to limit the locked position outside. According to the first variant, the pin for the elastic constriction has at least one longitudinal slot. In this case, the pin can consist of a hard-elastic or soft-elastic material, for example a metal or a plastic. A pin made of a flexible material, for example silicone rubber, a thermoplastic elastomer or rubber, can have sufficient elasticity for the elastic constriction even without a slit. According to the second variant, the pipette tip has at least one slot running in the longitudinal direction at the upper end for the elastic widening. In this case, the pipette tip can consist of a hard-elastic plastic, for example polypropylene or polyethylene, or of a soft-elastic plastic. It is also possible to produce a pipette tip, at least at the upper end, from a flexible material, for example silicone rubber, a thermoplastic elastomer or rubber, so that it has sufficient elasticity even without a slit for the elastic expansion. The pipette tip can be manufactured from several materials by multi-component injection molding. Here, the different materials can be positively and/or chemically connected to one another. The locking sleeve is designed in such a way that it does not deform when subjected to a radial force that is suitable for elastically narrowing the spigot and/or elastically widening the pipette tip. The locking sleeve consists, for example, of metal or of a hard-elastic or rigid plastic.

According to a further embodiment, the locking sleeve is arranged between the lifting rod and the pin and, in the locked position, limits the lower end of the lifting rod or the upper end of the tip piston on the outside and at the same time the pin on the inside, as a result of which the locking sleeve prevents detachment of a tip piston connected to the lifting rod in a form-fitting manner of the lifting rod and at the same time prevents a pipette tip, which is positively connected to the spigot, from detaching from the spigot. In this case, both the form-fitting connection of the tip piston with the lifting rod and the form-fitting connection of the pipette tip with the spigot are secured by the same locking sleeve. As a result, structural effort can be saved. In an alternative embodiment of the invention, the form-fitting connection of the tip piston with the lifting rod is secured by a first locking sleeve and the form-fitting connection of the pipette tip with the spigot is secured by a second locking sleeve. For this purpose, the second locking sleeve can delimit the spigot on the inside or delimit a pipette tip placed on the spigot on the outside.

According to a further embodiment, the locking sleeve and the ejector rod are connected to a gear mechanism, which includes the first operating element and the second operating element and is designed to control the displacement of the locking sleeve and the ejecting rod in opposite directions when at least one operating element is actuated, so that a form-fitting connection with the lifting rod connected tip piston by moving the ejector rod up and the locking sleeve downwards is prevented from detaching from the lifting rod and by moving the locking sleeve upwards and the ejector rod downwards the tip piston can be detached from the lifting rod and the pipette tip can be detached from the spigot. The transmission device enables a synchronized displacement of the locking sleeve and the ejector rod in opposite directions in order to either hold the tip piston and, if necessary, the pipette tip securely on the pipette or to release the secure hold of the tip piston and, if necessary, the pipette tip and detach them from the pipette . This makes it easier for the user to use the pipette tip with integrated tip plunger.

According to a further embodiment, the transmission device is designed to first move the locking sleeve upwards when pressing off a pipette tip and then to push off the tip piston from the lifting rod and the pipette tip from the attachment by moving the ejector rod downwards. In this way it can be achieved that the tip piston is pressed off the lifting rod and the pipette tip off the spigot only after the release of the form-fitting hold of the tip piston on the lifting rod and possibly the pipette tip on the spigot. According to another embodiment, the ejector rod is already pressing against the piston rod when the locking sleeve is still in the locking position.

According to another embodiment, the same control controls the displacement of the locking sleeve and the displacement of the ejector rod. In this embodiment, the first control element is also the second control element. According to a further embodiment, the same operating element controls the drive device. According to a further embodiment, the operating element drives the drive device.

This enables the pipette to be operated with one hand without having to change your grip. According to another embodiment, the pipette has an operating element for actuating the locking sleeve and the ejection device and an additional operating element, different from this operating element, for controlling the drive device.

According to another embodiment, the transmission device comprises a cam carrier mounted rotatably in the pipette housing, a first scanning element guided on a first cam on the circumference of the cam carrier, which protrudes from an ejector rod, which is guided in the pipette housing so that it can be displaced in the longitudinal direction of the spigot, a first scanning element on a second curve on the circumference of the cam carrier, which protrudes from a control rod which protrudes upwards from the locking sleeve and together with the locking sleeve forms a locking device which can be displaced in the direction of the pin in the pipette housing, and an operating element which protrudes from the pipette housing and can be rotated relative to the pipette housing. The cam carrier is designed in such a way that when the operating element is arranged in a starting position, the locking sleeve in a locking position delimits the lower end of the lifting rod or the upper end of the tip piston on the outside and, if necessary, delimits the pin on the inside and/or delimits the pipette tip on the outside, as a result of which the locking sleeve Detachment of a tip plunger connected in a form-fitting manner to the lifting rod and, if applicable, of a pipette tip connected in a form-fitting manner to the spigot, is prevented from the spigot, and the locking sleeve can be displaced upwards by turning the operating element, so that the lower end of the lifting rod or the upper end of the tip plunger is at least partially released and, if necessary, the spigot and/or the pipette tip is at least partially released and the ejection rod pushes the pipette tip off the spigot. The gear device with a cam carrier can be designed as in the parallel European patent application of today's date of the same applicant entitled "Pipette for use with a pipette tip" with the application number EP 19 150 808.4 described. In this respect, reference is made to the above patent application, the content of which is hereby incorporated into the present patent application.

According to a further embodiment, the drive device has a transmission mechanism which is designed to shift a drive element of the drive device alternately downwards and upwards during successive displacements of the operating element downwards, between which the operating element is displaced upwards. This type of embodiment is advantageous in the case of an operating element which can be displaced in the longitudinal direction of the pin in order to drive the drive device. The first time the control element is moved down, the drive element is moved from an upper position down to a lower position, with the subsequent movement of the control element up, the drive element maintains its lower position, and with the subsequent movement of the control element down, the Drive element shifted back to the upper position. This sequence can be repeated any number of times.

According to a further embodiment, the transmission mechanism is at least partially arranged within a curved carrier designed as a rotary sleeve. This enables space-saving accommodation.

According to a further embodiment, the pipette housing and the transmission device have a magnet arrangement and/or a spring device which is designed to automatically move the operating element into the starting position. The magnet arrangement includes, for example, two permanent magnets or one permanent magnet and a ferromagnetic component. The permanent magnets or the ferromagnetic component are held on the pipette housing and on the gear mechanism in such a way that they automatically shift the operating element into a starting position when they come closer to one another. This can also be achieved by a spring device which is preloaded when the gear device is displaced from the starting position and tends to shift the gear device back into the starting position.

According to a further embodiment, a scanning element is present coaxially to the spigot, which is supported by a spring on the pipette housing and can be preloaded by pushing a pipette tip onto the spigot, so that when a pipette tip is detached from the spigot, the spring relaxes and the scanning element is able to push the pipette tip off the pipette cones supported. The scanning element can in particular be a scanning element of a scanning device for scanning the collar of a pipette tip, as in FIG EP 18 168 763.3 described. In this respect, reference is made to the above patent application, the content of which is hereby incorporated into the present application.

According to a further embodiment, the pipette is a single-channel pipette or a multi-channel pipette. In the case of a multi-channel pipette, the cam carrier can control the ejector rod of a multi-channel ejector.

According to a further embodiment, the first means for positively connecting the lifting rod to the tip piston are a circumferential annular groove or a ring-shaped circumferential bead at the lower end of the lifting rod. According to a further embodiment, the first means for the form-fitting connection are formed on the inner circumference of a receptacle at the lower end of the lifting rod or on the outer circumference of the lifting rod. According to a further embodiment, the second means for the positive connection of the tip piston are designed to be complementary to the first means for the positive connection with the tip piston. According to a further embodiment, the second means for positively connecting the tip piston is a circumferential annular groove on the upper end of the tip piston or a ring-shaped circumferential bead on the upper end of the tip piston. According to a further embodiment, the further means for the positive connection are formed on the outer circumference of the tip piston or on the inner circumference of a receptacle at the upper end of the tip piston.

According to a further embodiment, the first means for the form-fitting connection of the spigot to a pipette tip are an annular groove running around the outside of the spigot or a bead running around the outside of the spigot in a ring-shaped manner. According to a further embodiment, the second means for positively connecting the pipette tip to the first means are designed to be complementary to the first means. According to a further embodiment, the second means for the positive connection of the pipette tip to the first means are a bead running around the inner circumference in a ring shape at the upper end of the pipette tip or an annular groove running around the inner circumference.

The lower end of the lifting rod denotes an area at the bottom of the lifting rod, which extends in the vertical direction over a more or less great length of the lifting rod. The upper end of the tip piston denotes an area at the top of the tip piston, which extends in the vertical direction over a greater or lesser length of the tip piston. The upper end of the pipette tip designates an area at the top of the pipette tip, which extends in the vertical direction over a more or less great length of the pipette tip.

Fig. 1

eine Direktverdrängerpipette mit auf dem Zapfen aufgesteckter Pipettenspitze teilweise geschnitten in einer Perspektivansicht;

Fig. 2

geschlitzter Zapfen mit innen anliegender Sperrhülse derselben Direktverdrängerpipette mit aufgesteckter Pipettenspitze in einer vergrößerten Perspektivansicht;

Fig. 3

dieselbe Anordnung in einer Seitenansicht;

Fig. 4

dieselbe Anordnung in einem Längsschnitt;

Fig. 5

Direktverdrängerpipette von Fig. 1 in einem Sprengbild;

Fig. 6

Direktverdrängerpipette von Fig. 1 in einem Sprengbild ohne Pipettengehäuse;

Fig. 7

Drehhülse mit der Abwurfstange und der Sperrhülse derselben Direktverdrängerpipette in der Ausgangsstellung in einer Perspektivansicht;

Fig. 8

dieselbe Direktverdrängerpipette in der Ausgangsstellung teilweise geschnitten in einer Seitenansicht;

Fig. 9

dieselbe Direktverdrängerpipette beim Pipettieren teilweise geschnitten in einer Seitenansicht;

Fig. 10

dieselbe Direktverdrängerpipette beim Abwerfen teilweise geschnitten in einer Seitenansicht;

Fig. 11

geschlitzte Pipettenspitze auf einem Zapfen einer anderen Direktverdrängerpipette mit einer außen an der Pipettenspitze anliegenden Sperrhülse in einem Längsschnitt;

Fig. 12a-e

Hubstange (Fig. 12a), Sperrhülse (Fig. 12b), Zapfen (Fig. 12c), Pipettenspitze (12d) und Spitzenkolben (Fig. 12e), jeweils in einer Seitenansicht;

Fig. 13a-c

unteres Ende der Hubstange (Fig. 13a), Hubstange eingesetzt in die Sperrhülse (Fig. 13b) und Hubstange und Sperrhülse eingesetzt in den Zapfen (Fig. 13c), jeweils in einer Perspektivansicht schräg von unten und von der Seite;

Fig. 14a-f

oberes Ende der Kolbenstange und unteres Ende der Hubstange vor dem formschlüssigen Verbinden (Fig. 14a), nach dem formschlüssigen Verbinden (Fig. 14b), nach dem Überschieben der Sperrhülse (Fig 14c), Pipettenspitze vor dem formschlüssigen Verbinden mit dem Zapfen (Fig. 14d), nach dem formschlüssigen Verbinden (Fig. 14e) und mit der Sperrhülse in Sperrstellung (Fig. 14f), jeweils in einer Seitenansicht.

The invention is explained below with reference to the attached drawings of an embodiment. In the drawings show:

1

a positive displacement pipette with a pipette tip attached to the spigot, partially sectioned in a perspective view;

2

slotted spigot with inner locking sleeve of the same positive displacement pipette with attached pipette tip in an enlarged perspective view;

3

the same arrangement in a side view;

4

the same arrangement in a longitudinal section;

figure 5

Positive displacement pipette from 1 in an explosive image;

6

Positive displacement pipette from 1 in an exploded view without pipette housing;

7

Rotating sleeve with the ejector rod and the locking sleeve of the same positive displacement pipette in the starting position in a perspective view;

8

the same positive displacement pipette in the starting position, partially sectioned in a side view;

9

the same positive displacement pipette during pipetting, partially sectioned in a side view;

10

the same positive-displacement pipette being ejected, partially sectioned in a side view;

11

slotted pipette tip on a spigot of another positive displacement pipette with a locking sleeve lying on the outside of the pipette tip in a longitudinal section;

Fig. 12a-e

lifting rod ( 12a ), locking sleeve ( Figure 12b ), cones ( Figure 12c ), pipette tip (12d) and tip plunger ( Figure 12e ), each in a side view;

Fig. 13a-c

lower end of the lifting rod ( 13a ), lifting rod inserted into the locking sleeve ( Figure 13b ) and lifting rod and locking sleeve inserted into the trunnion ( 13c ), each in a perspective view obliquely from below and from the side;

Fig. 14a-f

upper end of the piston rod and lower end of the lifting rod before positive connection ( 14a ), after the positive connection ( Figure 14b ), after pushing over the locking sleeve ( Figure 14c ), pipette tip before positive connection with the spigot ( Figure 14d ), after the positive connection ( Figure 14e ) and with the locking sleeve in locking position ( Fig. 14f ), each in a side view.

In the present application, the terms “above” and “below” as well as “vertical” and “horizontal” and terms derived therefrom such as “above” and “below”, “upright” and “upside down” and “ "Stacked" refers to an arrangement of the pipette in which the spigot is oriented vertically and is located at the downward-pointing end of the pipette body. With regard to the pipette tip, this information relates to a vertical orientation of the central axis of the pipette tip, with the tip opening being arranged at the bottom and the attachment opening at the top.

Based on Figures 1 to 10 an exemplary embodiment for securing a pipette tip on the spigot of a pipette by means of a locking sleeve limiting the spigot on the inside in the locked position is explained. Based on 11 an exemplary embodiment of securing a pipette tip on the spigot of a pipette by means of a locking sleeve delimiting the pipette tip on the outside is explained. Based on Figures 12 to 14 an exemplary embodiment for securing a tip piston on a lifting rod by means of a locking sleeve in the locking position outside the lower end of the lifting rod is explained. In this exemplary embodiment, the pipette tip is additionally secured on the spigot by the same locking sleeve, in that it delimits the spigot on the inside. The comments on the pipette from Figures 1 to 10 apply accordingly to the pipette according to Figures 12 to 14 .

According to 1 a pipette 1 designed as a direct displacement pipette has a rod-shaped (eg cylindrical) pipette housing 2 . A hollow-cylindrical shaft 3 projects downwards from the lower end of the pipette housing 2 . From the lower end of the shaft 3 is a pin 4 down, according to 1 and 4 a through hole 5 with a through hole at the lower end. The inner diameter of the through hole 5 is smaller than the inner diameter of the shank 3.

The spigot 4 has an upper spigot portion 6 in the shape of a hollow cylinder and below it a lower spigot portion 7 in the shape of a hollow cone. An annular groove 8 runs around on the outer circumference of the pin 4 between the upper pin section 6 and the lower pin section 7 .

The upper spigot section 6, the annular groove 8 and the lower spigot section 7 form first means for positively locking connection 9 of the pipette to a pipette tip.

Furthermore, the pin 4 has slots 10 running in its longitudinal direction, which are evenly distributed over the circumference. The slots 10 extend at the lower end 11 over the entire length of the pin 4.

According to 1 , 5 and 6 A drive device 12 is present in the pipette housing 2 , which comprises a transmission element 13 in the form of a transmission rod 14 , a transmission mechanism 15 and a drive element 16 in the form of a lifting rod 17 . Furthermore, the drive device 12 comprises an operating element 18 in the form of an operating lever 19 which is firmly connected to a carrier plate 21 via a web 20 .

According to 6 For example, the support plate 21 has an oval shape with a wide rounded end and a narrow rounded end, with the operating lever 19 protruding from the edge of the narrow rounded end. Adjacent to this edge, the support plate 21 has a first curved slot 22 which runs approximately parallel to the contour of the narrow rounded end. Further, the support plate 21 has a rectangular first edge recess 23 at the center of the first curved slot 22 on the side of the narrow rounded end.

According to 1 and 5 the lifting rod 17 is inserted into the shaft 3 and the pin 4 from above. According to 4 it is hollow and has an axial bore that extends to a hole in the lower end of the lifting rod. Furthermore, the Lifting rod 17 has a longitudinal slot 24 running from the lower end in the longitudinal direction. Due to the longitudinal slot 24, the lifting rod 17 has a C-shaped cross section. Its lower end forms a receptacle 25 for the upper end of a piston rod.

The transmission mechanism 15 is designed in such a way that with successive displacements of the operating lever 19 downwards, between which the operating lever 19 is displaced upwards, the lifting rod 17 is alternately displaced downwards and upwards. As a result, by pushing the operating lever 19 downwards, the lifting rod 17 can be shifted from an upper position to a lower position, the lifting rod 17 maintains the lowered position with the subsequent upward displacement of the operating lever 19, and the lifting rod 17 is moved by a subsequent pushing of the Operating lever 19 shifted down again up. This can be repeated any number of times.

According to 1 , 5 and 6 the pipette 1 is provided with a release device 26 . This comprises a curved carrier 27 which is rotatably mounted in the pipette housing 2 and is designed as a hollow-cylindrical rotary sleeve 28 . The rotary sleeve 28 is, for example, rotatably mounted with its outer circumference on the inner circumference of the pipette housing 2 and is supported at the upper and lower end between shoulders of steps on the inner circumference of the pipette housing 2, so that it cannot be displaced in the axial direction in the pipette housing 2. The axis of rotation of the rotating sleeve 28 coincides with the longitudinal axis of the pipette housing 2 and the longitudinal axis of the pin 4 .

The rotary sleeve 28 has on two diametrically opposite sides parallel to its axis of rotation recesses 29, 30 which extend from the upper edge of the rotary sleeve 28 and end at a distance from its lower edge. Below the recesses, the rotary sleeve 28 consists of a circular base 31 and above it consists of two diametrically opposite sectors 32, 33 of a circular ring, which delimit the two recesses 29, 30 laterally.

On the outer periphery of the circular base 31 of the rotary sleeve 28, a first cam 34 and a second cam 35 are arranged. The first cam 34 is formed as an inverted (upside down) Y-shaped first groove 36 . The vertical part 37 of the Y extends well up on a sector 32 to just short of the top edge of the sector 32. The second curve 35 is a second groove 38 on the outer periphery of the base 31 of the rotating sleeve 28 in the shape of an upright V. The first curve 34 and the second curve 35 are offset from one another by 80°, for example, on the circumference of the rotary sleeve. The first curve 34 and the second curve 35 each extend over an angular range of less than 90° over the circumference of the rotary sleeve 28.

According to 1 , 5 and 6 the ejection device 26 includes an ejection rod 39 which comprises a strip-shaped upper ejection rod part 40 and a cylindrical lower ejection rod part 41 . Instead of the ejection rod 39, a correspondingly bent, continuous wire can also be used. The upper and lower ejector rod parts 40, 41 are arranged parallel to one another and laterally offset from one another. The lower end of the upper ejector rod part 40 is connected to the upper end of the lower ejector rod part 41 via a strip-shaped connecting rod part 42 inclined obliquely to the two ejector rod parts. A first scanning element 43 in the form of a first guide pin 44 protrudes perpendicularly from the inside of the upper ejection rod part 40 . The ejection rod 39 is preferably formed in one piece, for example from a rigid plastic.

According to 1 , 4 and 7 if the ejection rod 39 is guided with the guide pin 44 in the first groove 36, the connecting rod part 42 extends through the longitudinal slot 24 of the lifting rod 17 and extends with the lower ejection rod part 41 inside the lifting rod 17 to just before the lower end thereof.

According to 1 , 4 , 5 and 6 the pipette 1 includes a locking device 45 which includes a locking sleeve 46 and a strip-shaped control rod 47 parallel thereto. The upper end of the locking sleeve 46 and the lower end of the control rod 47 are connected to each other via a second connecting rod part 48 which is inclined obliquely to the locking sleeve 46 and the control rod 47. A second sensing element 49 in the form of a second guide pin 49.1 protrudes from the inside of the control rod 47.

According to 1 and 7 the second guide pin 49.1 is guided in the second groove 38. According to 1 and 4 the locking sleeve 46 is inserted into the shank 3 from above and lies against the inside of the pin 4 . The lifting rod 17 and the ejection rod 39 are inserted into the locking sleeve 46 from above.

The operating element 18 is pushed with the first curved slot 22 onto the sector 32 of the rotary sleeve 28 on which the first groove 36 extends. According to 1 , 6 and 7 the rotary sleeve 28 is connected at the top to a support ring 50 which bridges the two sectors 32, 33 and stabilizes the rotary sleeve 28. The support ring 50 has a jacket 51 projecting downwards at the outer edge, which surrounds the two sectors 32, 33 laterally at the outer edges. It also has a second curved slot 52 which receives the upper edge of the sector 33 which is not provided with a groove 36,38. On the diametrically opposite side, there is a downwardly opening, rectangular second edge recess 52 .

The support ring 50 is connected to the rotary sleeve 28 by gluing, for example.

The rotating sleeve 28 and the locking sleeve 46 and the operating element 18 are made, for example, from one or more rigid plastics and/or from metal. The rotary sleeve 28, the support ring 50, the operating element 18 and/or the locking sleeve 46 are preferably each formed in one piece. A control button of Operating element 18 can also be made of an elastic or flexible plastic or rubber.

The operating lever 19 protrudes from the pipette housing 2 through a first housing slot which runs transversely to the longitudinal axis of the pipette housing 2 and extends over part of the circumference of the pipette housing 2, so that it can be operated from the outside. The first housing slot is connected in the middle to a second housing slot running in the longitudinal direction of the pipette housing 2 .

The operating lever 19 can be displaced downwards from the support ring 50 along the second housing slot against the action of a spring device, sliding with the first curved slot 22 on the sector 32 of the rotary sleeve 28 . After the load has been released, the spring device automatically moves the operating lever 19 back up.

A sleeve-shaped third scanning element 53 is guided on the outside of the shaft 3 . A spring device in the form of a helical spring 54 guided on the shaft is supported on the underside of the pipette housing 2 and on the upper side of the third scanning element 53 . The third scanning element 53 is pressed from above against a stop element on the shaft 3 or pin 4 by the coil spring 54 .

On the upper side of the pipette housing 2 there is a setting button 55 for setting a dosing volume. The dosing volume can be adjusted by turning the adjusting knob 55 . A counter 56 arranged underneath in the pipette housing 2 indicates the dosing volume set in each case. The setting button 55 and/or the counter 56 is coupled to the transmission mechanism 15 . The transmission mechanism 15 is designed to change the stroke of the lifting rod 17, which is carried out by moving the operating element 18 downwards, in accordance with the dosing volume set in each case.

According to Figures 1 to 4 a pipette tip 57 is attached to the pin 4 . The pipette tip 57 comprises a tubular body 58 having a tip opening 59 at the lower end, a collar 61 having a fitting opening 60 at the upper end, and a seating area 62 on the inner periphery of the collar 61 for clamping onto the spigot 4 . The seat area 62 has a contour complementary to the pin 4, which has a conical lower seat section 63 for receiving the conical lower pin section 7, a circumferential bead 64 above it for engaging in the annular groove 8 of the pin 4 and above this a cylindrical upper seat section 65 for receiving the cylindrical upper pin portion 6 has. The lower seat section 63, the bead 64 and the upper seat section 65 form second means for positively locking connection 66 of the pipette tip 57 to the pipette 1.

Below the seat area 62 the tubular body 58 has a cylindrical piston running area 67 . Below this, the tubular body 58 has a downwardly tapering tip portion 68 in the shape of a hollow truncated cone. The tip section 68 is in 4 shown and omitted in the remaining drawings for the sake of simplicity. A tip piston 69 is inserted in the tubular body 58 . This includes a piston 70 which is guided in the piston running area 67 . From the piston 70, a piston rod 71 having a smaller diameter than the piston 70 projects upward. The piston rod 71 has a piston head 72 at the upper end. The piston head 72 is according to 4 pressed down into the receptacle 25 of the lifting rod 17 .

The pipette 1 can be used as follows:
According to 1 and 8th a pipette tip 57 is held on the pipette 1 in a pipetting position. The seating area 62 is positively connected to the pin 4 in particular by the engagement of the bead 64 in the annular groove 8 . The operating element 18 is in the pipetting position at the upper end of the second housing slot, in which it can be rotated in both directions into the first housing slot. The maximum angle of rotation is limited by the circumferential extent of the first and second grooves 36, 38 or the first housing slot, whichever is less.

The locking sleeve 46 is in accordance with 4 arranged in the lowest position so that it prevents accidental detachment of the pipette tip 57 from the spigot 4. A radial constriction of the pin 4 would be required for the dissolution of the form-fitting connection, which the locking sleeve 46 does not permit in this position. The tip piston 69 is clamped with the piston head 72 in the receptacle 25 of the lifting rod 17.

To take up liquid, the pipette 1 is immersed in a liquid with the lower end of the pipette tip 57 held thereon. Thereafter, the operating element 18 is pressed down. This movement is converted into a lifting movement of the lifting rod 17 by the transmission device 15 . As a result, the tip piston 69 is displaced upward. Here, the piston head 72 takes the ejector rod 39 with it, so that the first guide pin 44 slides upwards in the vertical part 37 of the Y-shaped first groove 36 . Meanwhile, the locking sleeve 46 maintains its position. this is in 9 shown.

When the operating element 18 has executed the set stroke, the pipette tip 57 is filled with a certain amount of liquid. Thereafter, the operating element 18 is relieved and shifted back up by the spring device until it rests on the support ring 50 . To dispense this amount of liquid, the pipette 1 can be aligned with the pipette tip 57 towards another vessel. By pressing the operating element 18 down again, the lifting rod 17 is shifted down and the amount of liquid is dispensed. Here, the first guide pin 44 slides down to the node of the first groove 36.

When liquid is taken up, the operating element 18 executes an operating stroke that depends on the set amount of liquid. The operating stroke for dispensing the liquid is always the full operating path, regardless of the set amount of liquid.

The uptake and delivery of liquid can be carried out several times.

To eject the pipette tip 57, the operating lever 18 is pivoted to the right or to the left from the pipetting position. This rotates the rotary sleeve 28 so that the second groove 38 moves the second guide pin 49.1 and thus the locking sleeve 46 upwards until the locking sleeve 46 has released the pin 4 to such an extent that it can be deformed radially inwards. In the embodiment of Figures 12 to 14 In this case, the lower end of the lifting rod 17 is additionally released from the locking sleeve 46 to such an extent that it can be deformed radially outwards. For this purpose, the locking sleeve 46 is preferably pulled out of the through hole 5 . Furthermore, by turning the rotary sleeve 28, the first guide pin 44 is displaced downwards in one of the two lateral sections of the lower part of the first groove 36, so that the ejector rod 39 presses against the tip piston 69, which is supported on the tip section 68 at the bottom. Here, the bead 64 exerts a radial force on the pin, so that it narrows and the positive connection between the pipette tip 57 and the pin 4 is broken. As a result, the pipette tip 57 is released from the peg 4 . this is in 10 shown. In the embodiment of Figures 12 to 14 Here, the annular groove 77 or the thickening 75 exerts a radial force on the lifting rod 17 so that it expands and the form-fitting connection between the tip piston 69 and the lifting rod 17 is broken. The stripping of the pipette tip 57 from the peg 4 can also be assisted by the scanning element 53 which is pressed against the upper edge of the pipette tip 57 by the prestressed helical spring 54 .

When the used pipette tip 57 is detached from the spigot 4, a new pipette tip 57 can be connected to the spigot 4. For this purpose, the pipette 1 with the spigot 4 can be inserted into the receiving opening 68 of a pipette tip 57 held ready in a carrier. Here, the scanning element 53 is shifted upwards and the helical spring 54 is prestressed. Furthermore, the piston head 72 presses against the underside of the ejection rod 39 so that the first guide pin 44 slides up to the first branching point of the first groove 36 . Here, the rotary sleeve 28 is rotated in the pipette housing 2 until the operating element 18 is in the pipetting position. At the same time, the second guide pin 49.1 slides to the lowest point in the second groove 38. As a result, the locking sleeve 46 is in the locking position of 4 shifted, in which it prevents detachment of the pipette tip 57 from the pin 4. In the embodiment of Figures 12 to 14 In the locked position, the locking sleeve 46 also prevents the tip piston 69 from detaching from the lifting rod 17.

The connection of the tip plunger 69 to the lifting rod 17 and the pipetting can take place in the manner previously described.

The embodiment of 11 differs from that previously described in that the locking sleeve 46 is pushed over the outer circumference of the collar 61 of the pipette tip 57 in the locking position. In this direct displacement pipette, pipette tips 57 are used which have at least one longitudinal slit starting from the upper end. The longitudinal slit allows the pipette tip 57 to expand radially in order to establish the form-fit connection of the pipette tip 57 with the spigot 4 . The dissolution of the positive connection is prevented when the locking sleeve 46 is in the locking position, as in FIG 11 shown. To detach the pipette tip 57 from the spigot 4, the locking sleeve 46 is displaced upwards by means of the rotating sleeve 28, as in the previously described embodiment, and then the pipette tip 57 is detached from the spigot 4 by pressing against the upper side of the tip piston 69.

According to Figures 12a to e A pipette 1 comprises a pin 4 with slots 10 extending from the lower end, a lifting rod 17 with further slots 73 extending from the lower end and a locking sleeve 46 with a control rod 47 at the upper end. The pin 4 has a circumferential annular groove 8 in the area of the slots 10 .

In 12 A matching pipette tip 57 and a matching tip plunger 69 are also shown. The pipette tip 57 has a tubular body 58 with a tip opening 59 at the lower end and an attachment opening 60 at the upper end. The pipette tip 57 has a collar 61 with a seating area 62 on the inner circumference in which an inwardly projecting bead 64 runs.

Below the collar, the pipette tip 57 has a plunger running area 67 on the inside. This includes a piston 70 which is guided in the piston running area 67 .

A piston rod 71 which has a smaller diameter than the piston 70 projects upwards from the piston 70 . The piston rod 71 has a piston head 72 at the upper end.

Below the piston head 72, the piston 70 has a downwardly tapering cone 74 which is used to center the tip piston 69 at the top of the piston barrel portion 67 when it is inserted into the body 58 as far as it will go.

Above the cone 74, the piston head 72 has a cylindrical thickening 75 with a ramp 76 at the upper end. Under the thickening 75 another annular groove 77 runs around.

In 13a the lower end of the lifting rod 17 with the three slots 73 is shown enlarged.

The segments of the lift rod 17 remaining between the slots 73 have bottom inwardly projecting hooks 78 shaped and dimensioned to snap into the annular groove 77 on the piston head 72 .

According to Figure 13b the locking sleeve 46 is pushed onto the lifting rod 17 to over the beginning of the slots 73.

According to 13c this arrangement is inserted into the pin 4. The lifting rod 17, the locking sleeve 46 and the pin 4 are shaped and dimensioned in such a way that in 13c shown locking position of the locking sleeve 46, the lifting rod 17 in the area of the slots 73 can not be further elastically expanded and the pin 4 in the area of the slots 10 can not be further elastically compressed. When the hooks 78 engage in the annular groove 77 of the tip piston 69, the locking sleeve 46 thus prevents a tip piston 69 from becoming detached from the lifting rod 17.
A pipette tip held in the annular groove 8 of the spigot 4 on a bead 64 on the inner circumference of the body 58 is prevented from becoming detached by the locking sleeve 46 .

In 14 Figure 1 shows the upper end of tip piston 69 and the lower end of lift rod 17 prior to assembly. For assembly, the piston head 72 is inserted into the opening at the lower end of the lifting rod 17, the lower end of the lifting rod 17 being gradually expanded as the hooks 78 slide over the ramp 76. The elastic expansion of the locking sleeve 46 is facilitated by the slits 73 . Finally, the hooks 78 slide over the thickening 75 and snap into the further annular groove 77 . This is in the Figure 14b shown.

According to Figure 14c For example, the tip piston 69 is secured to the lift rod 17 by sliding the locking sleeve 46 over the lower end with the slots 73, since the locking sleeve 46 prevents elastic expansion of the lower end.

According to Figure 14d the pipette tip 57 is pushed onto the cone 4 with the push-on opening 60 until the bead 64 snaps into the annular groove 8 of the pin 4 . this is in Figure 14e shown.

According to Fig 14f the positive connection of the pipette tip 57 with the spigot 4 is secured by the locking sleeve 46, which is pushed into the area of the slots 10, 11. At the same time, the locking sleeve 46 ensures that the piston rod 71 is positively connected to the lifting rod 17.

The operation of a pipette, which corresponds to the components Figures 12 to 14 can be provided in the same way as the operation of the pipette according to Figures 1 to 10 be performed.

Reference list:

1

pipette

2

pipette housing

3

shaft

4

cones

5

through hole

6

upper trunnion section

7

lower trunnion section

8th

ring groove

9

first means for form-fitting connection

10

slot

11

lower end

12

drive direction

13

transmission element

14

transmission rod

15

transmission mechanics

16

drive element

17

lifting rod

18

control element

19

operating lever

20

web

21

backing plate

22

first curved slit

23

first edge recess

24

longitudinal slit

25

admission

26

discharge device

27

curve carrier

28

rotating sleeve

29

recess

30

recess

31

Base

32

sector

33

sector

34

first curve

35

second curve

36

first groove

37

vertical part

38

second groove

39

drop bar

40

upper ejection bar part

41

lower ejection bar part

42

connecting rod part

43

first sensing element

44

pilot

45

locking device

46

locking sleeve

47

control rod

48

second connecting rod part

49

second sensing element

49.1

second guide pin

50

support ring

51

coat

52

second curved slot

52.1

second edge recess

53

third sensing element

54

coil spring

55

adjustment knob

56

counter

57

pipette tip

58

body

59

lace opening

60

plug-in opening

61

collar

62

sitting area

63

lower seat section

64

bead

65

upper seat section

66

second means for form-fitting connection

67

piston running area

68

top section

69

top piston

70

Pistons

71

piston rod

72

piston head

73

slot

74

cone

75

thickening

76

ramp

77

ring groove

78

hook

Claims (11)

Pipette for use with a pipette tip comprising an integral tip plunger • a rod-shaped pipette housing (2), • a pin (4) at the lower end of the pipette housing (2) for holding a pipette tip (57), • a lifting rod (17) for moving the tip plunger (69) in the pipette tip (57), the lifting rod (17) having a receptacle (25) at its lower end for inserting the upper end of the tip plunger (69) on the pin ( 4). the pipette tip (57) held on the spigot (4) and engaging with the tip piston (69) in a through hole (5) of the spigot can be inserted, • the lifting rod (17) at the lower end having first means for positively connecting (78) the lifting rod (17) to the tip piston (69) and the upper end of the lifting rod (17) having second means for positively connecting (77) the tip piston (69 ) with the first means, so that the tip piston (69) can be inserted into the receptacle (25) of the lifting rod (17) with elastic expansion of the lower end of the lifting rod (17) before the positive connection with the lifting rod (17), or the the lifting rod (17) can be inserted into the receptacle of the tip piston (69) with elastic expansion of the upper end of the tip piston (69) before the positive connection with the tip piston (69), • a drive device (12) for displacing the lifting rod (17) for sucking in a liquid sample into one held on the pin (4). Pipette tip (57) and ejection of the sample from the pipette tip (57) by means of a tip plunger (69) positively connected to the lifting rod (17), • at least one locking sleeve (46) which is arranged coaxially to the lifting rod (17) and which can be displaced in the direction of the lifting rod (17) in the pipette housing (2), • wherein the at least one locking sleeve (46) can be moved into a locking position in which it holds a lower end of the lifting rod (17) that can be expanded by inserting the upper end of a pointed piston (69) into the receptacle (25) of the lifting rod (17) or a by inserting the lower end of the lifting rod (17) into a receptacle of the lifting rod (69), the expandable upper end of the lifting rod (69) is delimited on the outside, as a result of which the locking sleeve (46) prevents detachment of a lifting rod (17) connected to the lifting rod (17) in a form-fitting manner. prevented by the lifting rod (17), and the locking sleeve (46) can be moved upwards out of the locking position, so that the lifting rod (17) or the upper end of the tip piston is at least partially released and the tip piston (69) is released from the lifting rod (17). is removable. Pipette according to Claim 1, in which the lifting rod (17) has at least one slot (73) running in the longitudinal direction and the locking sleeve (46) in the locking position delimits the lifting rod (17) on the outside in the region of the slot (73) or the locking sleeve (46 ) is designed to delimit a top piston (69) which has at least one slot running in the longitudinal direction at the upper end and is positively connected to the lifting rod (17) in the blocking position of the piston rod (71) in the region of the slot. Pipette according to Claim 1 or 2, in which the locking sleeve (46) is connected to a first operating element (17) which protrudes from the pipette housing (2) and can be displaced relative to the pipette housing (2), in order, by actuating the first Operating element (17) to move the locking sleeve (46) down into the locked position and out of the locked position up. Pipette according to one of Claims 1 to 3, which has an ejection device (26) which comprises an ejection rod (39) which is displaceably guided in the longitudinal direction of the spigot (4) within an axial bore of the lifting rod (17) and with its lower end above of the tip piston (69) when this is positively connected to the lifting rod (17) and comprises a second operating element (18) connected to the ejection rod (39) in order to displace the ejection rod (39), the ejection device (26) designed to push the tip piston (69) off the lifting rod (17) by moving the ejection rod (39) downwards and to push the pipette tip (57) surrounding the tip piston (69) off the spigot (4) when the locking sleeve (46) Lifting rod (17) or the upper end of the tip piston (69) at least partially releases. Pipette according to one of Claims 1 to 4, in which the spigot (4) has first means for positively connecting (9) the spigot (4) to a pipette tip (57), such that a pipette tip (57) has the second means for positively locking (66) of the pipette tip with the first means for positively connecting (9) the spigot, with elastic narrowing of the spigot (4) and/or with elastic widening of the pipette tip (57) before its positive connection with the spigot (4) on the peg (4), at least one locking sleeve (46) is arranged coaxially with the peg (4) and is guided in the pipette housing (2) so that it can be displaced in the direction of the peg (4), the at least one locking sleeve (46) being displaceable into a locking position , in which it delimits a peg (4) that can be narrowed by sliding a pipette tip (57) on the inside and/or a pipette tip (57) that can be widened by pushing onto the peg (4) on the outside, whereby the locking sleeve ( 46) a detachment of a pipette tip (57) connected in a form-fitting manner to the spigot (4) from the Pin (4) is prevented and the locking sleeve (46) can be moved upwards out of the locked position, so that the pin (4) and/or the pipette tip (57) is at least partially released and the pipette tip (57) can be detached from the pin (4). is. Pipette according to Claim 5, in which the spigot (4) has at least one slot (10, 11) running in the longitudinal direction and the locking sleeve (46) delimits the spigot (4) on the inside in the locking position and/or in which the locking sleeve (46) is designed to externally delimit a pipette tip (57) in the blocking position, which has at least one slot running in the longitudinal direction at the upper end and is positively connected to the spigot (4). Pipette according to Claim 5 or 6, in which the locking sleeve (46) is arranged between the lifting rod (17) and the spigot (4) and in the locking position the lower end of the lifting rod (17) or the upper end of the tip piston (69) outside and at the same time limits the pin (4) on the inside, as a result of which the locking sleeve (46) prevents a tip piston (69) which is positively connected to the lifting rod (17) from detaching from the lifting rod (17) and at the same time a detachment of a form-locking connection with the pin (4 ) connected pipette tip (57) prevented from the pin (4). Pipette according to one of Claims 4 to 7, in which the locking sleeve (46) and the ejector rod (39) are connected to a transmission device which comprises the first operating element (18) and the second operating element (18) and is designed, when actuated, at least an operating element (18) to control the displacement of the locking sleeve (46) and the ejector rod (39) in opposite directions, so that a top piston (69) positively connected to the lifting rod (17) by moving the ejector rod (39) upwards and the locking sleeve (46) is prevented from detaching from the lifting rod (17) down and by moving the locking sleeve (46) up and the The ejection rod (39) can be detached downwards, the tip piston can be detached from the lifting rod (17) and the pipette tip (57) can be detached from the pin (4). Pipette according to Claim 8, in which the gear mechanism is designed, when a pipette tip (57) is pressed off, first to displace the locking sleeve (46) upwards, then, by displacing the ejection rod (39) downwards, the tip piston (69) from the lifting rod (17) and push off the pipette tip (57) from the spigot (4). Pipette according to Claim 8 or 9, in which the same operating element (18) controls the displacement of the locking sleeve and the displacement of the ejection rod (39). Pipette according to one of Claims 1 to 10, in which the same operating element controls the drive device (12).

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