EP2633915B1 - Pipette with calibration system - Google Patents

Description

The invention relates to a pipette for exchangeable pipette tips.

Pipettes are used especially in the laboratory for dosing liquids. For this purpose, a pipette tip with an upper opening is clamped on a seat of the pipette. The seat is usually a conical or cylindrical projection relative to a housing of the pipette, on which a pipette tip can be clamped with the upper opening. Through a lower opening, the pipette tip can absorb and dispense liquid. Bubble pipettes include an air displacement device communicating with the pipette tip through a hole in the seat. By means of the displacement device, an air cushion is displaced, so that liquid is sucked into the pipette tip and ejected therefrom. For this purpose, the displacement device has a displacement chamber with a displaceable boundary. The displacement device is usually a cylinder with a piston displaceable therein.

The pipette tips are released from the seat after use and replaced with a fresh pipette tip. As a result, contamination can be avoided at subsequent dosages. In most cases, pipette tips have a discharge device for ejecting the pipette tips, which allow ejection by button operation without touching the pipette tips. Single-use pipette tips are available inexpensively from plastic.

The displaceable boundary is coupled to a drive device which serves to displace the piston in the cylinder. The drive device has a lifting rod, which with a stop element between an upper and a lower stop is displaceable. At the beginning of the suction of air into the displacement chamber, the stop element is located at the lower stop. At the beginning of the displacement of air from the cylinder, the stop element is located at the top stop. The absorbed or dispensed amount of liquid depends on the stroke of the movable limit and thus from the stroke of the lifting rod. The stroke volume of the displaceable boundary does not correspond exactly to the amount of liquid absorbed and dispensed. Since the air column lengthens slightly under the weight of the liquid, the stroke volume exceeds the liquid volume. The deviation of stroke volume and liquid volume depends in particular on the density and viscosity of the liquid, the temperature, the air pressure and wetting effects. It is known, for example from the WO 03/033151 or US-A-3,827,305 To calibrate pipettes by adjusting the position of an upper stopper body to a specific dosing volume.

For fixed volume pipettes, the distance between the top and bottom stops is constant. From the US 4,020,698 is a fixed volume pipette with an upper stop body in the form of an adjustable by means of a calibration tool threaded sleeve known.

For pipettes with adjustable dispensing volume, the position of the top stop is variable. Known pipettes have an upper stop body in the form of a threaded spindle which is adjustable in a fixedly arranged in the housing spindle nut. To adjust the threaded spindle adjusting devices are available, which are coupled with display devices for displaying the set metering volume in the form of a counter. The DE 43 35 863 C1 describes a pipette in which the display devices for calibration can be decoupled from the setting devices.

In the case of the known pipettes, factory calibration is carried out by the pipette manufacturer under standard conditions. This double-distilled water is pipetted at a temperature of 20 to 25 ° C and an air pressure of 1013 mbar. For pipetting under different conditions, the user must change the factory calibration. Changing the factory calibration and later retrieving the factory calibration is expensive.

The EP 1 743 701 B1 describes a pipette in which the lower stopper body is held in a holder. Between the lower stopper body and the holder, an overstroke spring is arranged. In addition, adjusting means for adjusting the position of the holder with respect to the cylinder is provided. A display device displays the respective position of the holder. This pipette allows the user to easily calibrate, for example, when metering a liquid that has a different density or viscosity than double-distilled water, or when working at a different air pressure or temperature. The user calibration is carried out exclusively by adjusting the lower stop body. The adjustment made in the factory calibration of the upper stop body and the display devices is not changed. The display device displays the respective position of the lower stop body. The position taken by the lower stop body during factory calibration can be easily retrieved at any time.

In a practical embodiment, the holder is screwed coaxially to the lifting rod in a fixedly arranged in the housing carrier. A coaxially arranged to the lifting rod indicator ring with a bevel gear at the top is rotatably mounted in the carrier. From the indicator ring are upwards parallel to the lifting rod driving pins before, in the axial direction in holes in the bottom of the engage cup-shaped holder. On the carrier, a pinion is rotatably mounted, which meshes with the bevel gear and has a hexagon socket in one end face. A tool is insertable through a hole in the housing in the tool engagement to rotate the pinion. In this case, the display ring is rotated, which rotates about the driving pins with the holder. Since the holder is screwed into a thread of the carrier, this changes the axial position of the holder in the carrier and thus the axial position of the lower stopper body. The change in the axial position of the holder with respect to the indicator ring is compensated by the variable depth of engagement of the driving pins in the driving holes.

In the known device for user calibration, the calibration accuracy is impaired due to manufacturing tolerances and wear of the many components. In addition, the production costs are high due to the many components.

On this basis, the present invention seeks to provide a less expensive pipette that allows the user a user calibration independent of the factory calibration with better calibration accuracy.

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

• ein stangenförmiges Gehäuse,
• einen Sitz zum lösbaren Halten einer Pipettenspitze am unteren Ende des Gehäuses,
• eine Verdrängungseinheit umfassend eine Verdrängungskammer mit einer verlagerbaren Begrenzung,
• einen die Verdrängungskammer mit einer Öffnung im Sitz verbindenden Verbindungskanal,
• eine mit der verlagerbaren Begrenzung gekoppelte, eine axial verlagerbare Hubstange aufweisende Antriebseinrichtung zum Verlagern der verlagerbaren Begrenzung der Verdrängungskammer,
• einen oberen Anschlagkörper, einen unteren Anschlagkörper und ein Anschlagelement am Umfang der Hubstange zum Begrenzen des Hubes der Hubstange,
• eine Überhubfeder, über die der untere Anschlagkörper entgegen einer Verlagerung nach unten an einem Überhubfederlager abgestützt ist,
• ein mit dem Gehäuse fest verbundenes, feststehendes Schraubelement und ein damit in Eingriff stehendes, im Gehäuse verlagerbares Schraubelement, das mit dem unteren Anschlagkörper gekoppelt ist, um diesen bei einer Verlagerung des verlagerbaren Schraubelementes in axialer Richtung der Hubstange zu verlagern,

gekennzeichnet durch

• eine entlang einer Schraubenlinie mit derselben Steigung wie das Gewinde des verlagerbaren Schraubelementes verlaufende Verzahnung mit in Richtung der Schraubachse gerichteten Zähnen am oberen Rand des verlagerbaren Schraubelementes,
• ein drehbar auf einem fest mit dem Gehäuse verbundenen Lager gelagertes Antriebszahnrad, das mit der axialen Verzahnung des verlagerbaren Schraubelementes kämmt und
• Mittel zum Verdrehen des Antriebszahnrades.

The pipette according to the invention has

• a rod-shaped housing,
• a seat for releasably holding a pipette tip at the lower end of the housing,
• a displacement unit comprising a displacement chamber with a displaceable boundary,
• a connecting channel connecting the displacement chamber to an opening in the seat,
• a coupled to the movable boundary, an axially displaceable lifting rod having drive means for displacing the displaceable boundary of the displacement chamber,
• an upper stop body, a lower stop body and a stopper member on the periphery of the lift rod for limiting the stroke of the lift rod,
• an overstroke spring, via which the lower stop body is supported against a displacement downwards on an overstroke spring bearing,
• a fixed screw element fixedly connected to the housing and a screw element displaceable in the housing and coupled thereto, which is coupled to the lower stop body in order to displace it in a displacement of the displaceable screw element in the axial direction of the lift rod,

marked by

• a toothing running along a helix with the same pitch as the thread of the displaceable screw element with teeth directed in the direction of the helical axis at the upper edge of the displaceable screw element,
• a rotatably mounted on a bearing fixedly connected to the housing bearing drive gear, which meshes with the axial toothing of the movable screw element and
• Means for rotating the drive gear.

In the pipette according to the invention, the lifting rod is displaceable with the stop element between the upper stop body and the lower stop body. As a result, the stroke of the lifting rod and the movable limit is limited and determines the dosing. In addition, the lower stop body is over a Supports overstroke spring, so that overcoming the spring force of the overstroke spring an overstroke to blow out residual liquid from a pipette tip is possible. For a user calibration, the lower stop body is adjustable. For this purpose, the displaceable screw element is displaceable on the fixed screw, which displaces the lower stop body in the axial direction of the lifting rod during the displacement. As a result, the stroke of the lifting rod and the movable limit is changed.

To drive the displaceable screw this has at the top of a toothing with teeth that are directed parallel to the screw axis of the movable screw. The toothing extends along a helical line which has the same pitch as the thread of the displaceable screw element, which engages with the thread of the fixed screw element. The mounted on a firmly connected to the housing bearing drive gear meshes with the teeth. When rotating the drive gear by means for rotating the movable screw is screwed into the fixed screw and thus axially displaced. Due to the fact that the teeth of the displaceable screw element run along a helix with the same pitch as the thread of the displaceable screw element, in this case the toothing remains in engagement with the drive gearwheel. Due to this construction, components are saved compared to the conventional means for user calibration. As a result, the error sources are reduced and increases the calibration accuracy. In addition, the cost of manufacturing and manufacturing costs are reduced.

According to one embodiment, the displaceable screw is a concentric with the lifting rod arranged threaded ring with a thread on the circumference, the top having the teeth and is seated on the bottom of the lower stop body. The screw ring can be accommodated to save space in the housing and can sit evenly with its lower edge on the lower stop body.

According to a further embodiment, the fixed screw is a hollow cylindrical lifting body, which has an external thread on the outer circumference with an internal thread on the inner circumference of the screw is engaged, the lifting body has a plurality of axially extending slots, the lower stop body is arranged in the lifting body and For example, the lower stopper body has a plurality of outwardly projecting projections, which pass through the slots and have protruding portions from the lifting body on which the threaded ring is seated. This allows a space-saving arrangement of the fixed screw and the lower stop body.

According to a further embodiment, the overstroke spring bearing is arranged in the lifting body and the overstroke spring arranged in the lifting body between the lower stopper body and overstroke spring bearing. As a result, over-stroke spring bearing and over-travel spring are accommodated to save space. The lifting body additionally saves space as a receptacle and support for the overstroke spring bearing and the overstroke spring.

In an embodiment of the pipette as a fixed-volume pipette, the upper stop body is fixedly arranged in the housing. In a pipette with adjustable metering volume of the upper stop body is arranged displaceably in the housing in the axial direction of the lifting rod. According to a preferred embodiment, the upper stopper body is a threaded spindle, which is screwed into a fixedly connected to the housing spindle nut and having an upper passageway through which the lifting rod is passed and / or is the lower Stopper body circular disk-shaped and has a lower passageway through which the lifting rod is extending therethrough.

According to a further embodiment, the lifting body is fixedly connected at the top with the spindle nut. This allows a space-saving accommodation of the means for adjusting the dosing volume. The lifting body serves as a receptacle and support for the mother, spindle and lifting rod, which is inserted into the upper through hole and is displaceable with the stop element between the upper and lower stop body.

According to a further embodiment, the bearing of the drive gear is fixedly connected to the lifting body above the external thread. In this embodiment, the lifting body also serves as a carrier of the drive gear.

When mounting the pipette, the lifting body can be equipped separately with the various components. The populated lifting body is an assembly that is completely mountable in the housing.

According to a further embodiment, the lifting body is connected by a snap connection with the housing. As a result, the lifting body is firmly connected to the housing in a simple manner. Optionally, the snap connection for disassembly of the lifting body can be selectively resolved.

According to a further embodiment, the drive gear and the displaceable screw element are bevel gears or crown wheels.

According to another embodiment, a display device for indicating the position of the lower stopper body is present.

According to a further embodiment, the screw ring on the outer circumference in the circumferential direction spaced apart markings and the housing has a window for reading a arranged under the window mark. The markings serve to indicate to the user the respective setting of the displaceable screw element and thus of the lower stop body. In a preferred embodiment, a special mark is present, indicating to the user that the lower stop body has assumed the position in which the factory calibration has been carried out. On both sides of this central mark there may be further markings indicating the deviation of the position of the lower stop body from the factory calibration in both directions.

According to a further embodiment, the markings are arranged on the circumference of the screw ring on a helical line whose pitch corresponds to the pitch of the thread of the displaceable screw element. This ensures that the various markings are always visible at the same point in the window during rotation of the displaceable screw despite the associated axial change in position of the movable screw.

According to a further embodiment, the drive gear has a tool engagement for rotating the drive gear and the housing has a hole through which the tool attack is accessible by means of a tool introduced from outside into the hole. The user can make the user calibration specifically by applying a tool to the tool attack and turning the tool in different directions. The tool attack is for example a slot, Phillips, Torx, hexagon socket or other polygon socket.

In a further embodiment, means are provided for limiting the twisting of the displaceable screw element, which prevent the highest tooth of the toothing from being released from the drive gearwheel. The highest tooth of the axial toothing is the tooth which is arranged on the highest position of the helix along which the toothing of the displaceable screw element runs. The limitation prevents the toothing from being released from the drive gear.

The limitation is, for example, a radially protruding projection of the displaceable screw element which strikes a projection arranged fixedly in the housing when the drive gear reaches the highest tooth of the toothing. According to a preferred embodiment, the toothing of the displaceable screw element adjacent to the highest tooth is limited by a parallel to the screw axis directed axial projection which blocks the drive gear at the end of the toothing. To block the drive gear, the axial projection has no teeth and is made solid so that the drive gear can not be rotated past it. When the drive gear engages the deepest tooth of the toothing, further rotation of the displaceable screw element is prevented by the step having the toothing to the adjacent highest tooth out.

The pipette according to the invention is preferably a hand-held pipette. This is a pipette that can be held and operated by a user when pipetting with just one hand. Preferably, the pipette is a mechanically driven pipette. In principle, it is also possible to form the pipette with an electric drive or a mechanical drive with power assistance by an electric drive (servo drive).

Fig. 1

eine erfindungsgemäße Pipette in einem Längsschnitt;

Fig. 2

dieselbe Pipette in einem vergrößerten Längsschnitt durch einen oberen Teil;

Fig. 3

ein vergrößerter Schnitt entlang der Linie III - III von Fig. 2;

Fig. 4

vergrößertes Detail IV von Fig. 2;

Fig. 5

dieselbe Pipette in einem vergrößerten Längsschnitt durch einen unteren Teil;

Fig. 6

dieselbe Pipette ohne Hubkörper in einem vergrößertem Längschnitt durch einen unteren Teil;

Fig. 7

Baugruppe umfassend Hubkörper, Gewindespindel, unteren Anschlagkörper, Überhubfeder und Bauteile für Anwenderkalibrierung in Seitenansicht;

Fig. 8

dieselbe Baugruppe in einem Vertikalschnitt;

Fig. 9

dieselbe Baugruppe in einer Perspektivansicht von der zu Figur 7 entgegengesetzten Seite;

Fig. 10a bis d

dieselbe Pipette vor dem Betätigen des Betätigungselement (Fig. 10a), nach dem vollständigen Ausführen des Dosierhubes und vor Ausführung des Überhubes (Fig. 10b). nach dem Ausführen des Überhubes vor dem Abwerfen der Pipettenspitze (Fig. 10c) und nach dem Abwerfen einer Pipettenspitze (Fig. 10d) jeweils in einem teilweisen Längsschnitt.

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

Fig. 1

a pipette according to the invention in a longitudinal section;

Fig. 2

the same pipette in an enlarged longitudinal section through an upper part;

Fig. 3

an enlarged section along the line III - III of Fig. 2 ;

Fig. 4

enlarged detail IV of Fig. 2 ;

Fig. 5

the same pipette in an enlarged longitudinal section through a lower part;

Fig. 6

the same pipette without lifting in an enlarged longitudinal section through a lower part;

Fig. 7

Assembly comprising lifting element, threaded spindle, lower stop element, overstroke spring and components for user calibration in side view;

Fig. 8

the same assembly in a vertical section;

Fig. 9

the same assembly in a perspective view of the FIG. 7 opposite side;

Fig. 10a to d

the same pipette before operating the actuator ( Fig. 10a ), after complete execution of the metering stroke and before execution of the overstroke ( Fig. 10b ). after performing the overtravel before dropping the pipette tip ( Fig. 10c ) and after dropping a pipette tip ( Fig. 10d ) each in a partial longitudinal section.

In the present application, the terms "up" and "down", "above" and "below" and "horizontally" and "vertically" refer to an orientation of the pipette in which the housing is vertically aligned with the seat. In this orientation, a pipette tip mounted on the seat can be directed to an underlying vessel to aspirate or dispense liquid.

According to Fig. 1 and 2 the pipette 1 has a rod-shaped, molded as a handle housing with an upper housing part 2 and a lower housing part 3. The upper housing part 2 with all the parts included forms a drive unit and the lower housing part 3 with all parts contained a displacement unit. From the upper housing part 2 is above an actuator 4 in the form of a cylindrical push button out. The actuating element 4 is mounted axially displaceably and rotatably in the upper housing part 2.

The actuating element 4 is screwed with a thread in a cover 5 on a cylindrical lifting rod 6. The lifting rod 6 is passed in the upper housing part 2 through an upper passage channel 7 of a threaded spindle 8. The threaded spindle 8 is screwed into an internal thread of a housing upper part 2 held in a defined position spindle nut 9.

The spindle nut 9 is fixedly connected to a lifting body 10 which is fixed in the upper housing part 2. The lifting body 10 is substantially cylindrical and is a support for the spindle nut 9, the threaded spindle 8 screwed therein and the lifting rod 6 guided therein. During assembly of the pipette, these and other components are preassembled on the lifting body 10 and the lifting body 10 equipped with the components is mounted in the upper housing part 2, so that it is firmly held in the upper housing part 2. For this purpose, the lifting body 10 is locked to the upper housing part 2. In principle, it is also possible to mount the components preassembled on the lifting body 10 directly in the upper housing part 2. For this purpose, the upper housing part 2 can be equipped inside corresponding to the lifting body 10.

The threaded spindle 8 has a rotatably connected thereto Spindelmitnehmer 11 above. The Spindelmitnehmer 11 has on the circumference a hexagon 12 with a central hole 13. The hexagon 12 engages in a Innsensechskant 14 of the actuating element 4 a.

The actuator 4 is provided at the bottom with two diametrically opposed, radial projections 15, 16 which project outwardly. Preferably, four radial projections 15, 16 are present. The radial projections 15, 16 engage in axially extending grooves 17, 18 on the inside of a hollow cylindrical transmission part 19, which is rotatably mounted in the upper housing part 2. The transmission member 19 has at the top of the outer circumference a sprocket 20 which meshes with a gear of a counter gear 21 which drives a plurality of juxtaposed on a horizontal axis counter wheels 22 of a counter 23. The counter 23 is attached to the upper housing part. The Zählwerksräder 22 each have digits from 0 to 9. Das - based on Fig. 1 - The last counter gear 22 is driven by the counter gear 21. The next one arranged counting wheels 22 are further rotated in each case by one digit when the behind arranged Zählwerksrad passes from 9 to 0.

Above the counter 23, the upper housing part 2 has a housing cover 24 with a window through which the digits of the counter wheels 22 can be read.

Below the threaded spindle 8, a beaded collar 25 is arranged as a stop element on the lifting rod 6. The displacement of the lifting rod 6 upwards is limited by contact of the collar 25 at the lower end face 26 of the threaded spindle 8, which forms an upper stop body for the collar 25.

Below the spindle nut 9, a substantially disc-shaped lower stop body 27 is arranged in the lifting body 10. The lower stop body 27 has a cup-shaped depression, in which a central passageway 28 is arranged centrally. Further, the lower stopper body 27 has a plurality (e.g., three or four) radially outwardly projecting protrusions 29 evenly distributed around its circumference.

The lower stop member 27 is guided on the projections 29 in axially extending guide slots 30 of the lifting body 10. This is also in Fig. 3 shown. Upwards he is 30 until the projection of the projections 29 at the upper end of the guide slots 30 displaced.

Below the lower stop body 27, a lifting spring 31 designed as a helical spring is arranged in the lifting body 10. At the top, the overstroke spring bears against the lower side of the lower stop body 27. Bottom supports the overstroke spring 31 is arranged on an upper part of the housing 2 and thus fixedly connected over-stroke spring bearing 32.

The over-stroke spring bearing 32 is formed by a ring with L-section, wherein the horizontal leg of the L-profile surrounds a central through hole 33 of the overstroke spring bearing 32. The overstroke spring 31 is supported on the horizontal leg of the L-profile and is laterally bordered by the vertical leg. The overstroke spring 31 presses the lower stopper body 27 with the protrusions 29 under bias against the upper ends of the guide slots 30.

Below the lower stopper body 27, a drive element 34 in the form of a coaxial with the lifting rod 6 aligned sleeve is present in the lifting body 10. The drive member 34 has an upper sleeve portion 35 and a lower sleeve portion 36, wherein the upper sleeve portion 35 has larger inner and outer diameter than the lower sleeve portion 36. The lower sleeve portion 36 has a frusto-conical tip 37 at the bottom.

At the upper edge of the upper sleeve portion 35, a radially outwardly projecting, further circumferential collar 38 is present. The outer diameter of the upper sleeve portion 35 is smaller than the inner diameter of the through hole 33 of the overstroke spring bearing 32, so that the lower and the upper sleeve portion 35, 36 are insertable into the through hole 33. The outer diameter of the further collar 38 exceeds the inner diameter of the through-hole 33, so that the drive element 34 can not completely pass through the through-hole 33. The over-stroke spring bearing 32 forms an end stop and the further collar 38 an end stop element, which limit the displacement of the drive element 34 down.

In the upper sleeve portion 35, a hollow cylindrical armature 39 is arranged from a ferromagnetic material above. Below this, a hollow cylindrical magnet 40 is arranged in the upper sleeve section 35. Below this is a pot 41 which receives the magnet 40. The armature 39 has an interference fit in the upper sleeve portion 35. The lifting rod 6 extends slidably through the central hole of the armature 39 therethrough. Below the armature, the lifting rod 6 has a needle-shaped portion 42 of reduced diameter. The magnet 40 and the pot 41 are seated on the needle-shaped portion 42. Preferably, the magnet 40 and pot 41 are fixed on the needle-shaped portion 42, e.g. by having a press fit there. In addition, the magnet 40 is supported at the top on a shoulder of the lifting rod from which the needle-shaped portion 42 extends.

Below the pot 41 a trained as a helical spring decoupling spring 43 is guided on the needle-shaped portion 42, which is supported at the bottom bottom of the lower sleeve portion 36. Armature 39, magnet 40 and decoupling spring 43 are components of a decoupling device 44.

According to FIG. 1 . 2 . 5 and 6 is the upper housing part 2 below next to a lower housing opening 45 on the inner circumference with unspecified means for releasably connecting 46 with further means for releasably connecting the housing base 3 is provided.

The lower housing part 3 has a hollow cylindrical section 47 at the top, followed by a short upper hollow cone section 48 with a large cone angle, followed in turn by a long lower hollow cone section 49 with a small cone angle, with its lower end a conical projection 50 for clamping a pipette tip 51 forms. A clamped pipette tip 51 is also substantially conical with an upper opening 52 for attachment to the lug 50 and a lower opening 53 for the passage of liquid. The upper opening 52 is substantially larger than the lower opening 53 and from the upper to the lower opening, the pipette tip 51 tapers.

The hollow cylindrical portion 47 of the lower housing part 3 is provided at the top of the outer circumference with other means for releasable connection 54, which are not described in more detail, which are adapted to the means for releasably connecting 46 of the upper housing part 2 to releasably connect the lower housing part 3 with the upper housing part 2. Suitable means for releasably connecting 46, 54 of the upper housing part 2 and lower housing part 3 are in the DE 10 2004 003 434 B4 described. In this regard, reference is made to the DE 10 2004 003 434 B4 and US2005 / 155438 A1 , the content of which is hereby incorporated into this application.

The lower hollow cone section 49 has at the top a projection 55 projecting beyond the upper hollow cone section 48 in the lower housing part 3.

The lower hollow cone portion 49 has a connecting channel 56 which connects the upper end face of the extension 55 with the lower end face of the projection 50.

In the lower housing part 3, an arrangement of a cylinder 57 is arranged with a displaceable piston 58 therein. The cylinder 57 is inserted with a lower portion in the connecting channel 56 and fixed therein by press-fitting or gluing. At the bottom, the cylinder 57 is sealed off from the connecting channel 56 by means of an O-ring 59.

The piston 58 has on the circumference a piston seal 60, which seals on the inside of the cylinder 57. Below the piston seal 60, the piston 58 has a needle-shaped Extension 61, which is insertable into a through hole 62 in the bottom of the cylinder 57 and in the connecting channel 56 in order to reduce the dead volume. Cylinder 57 and piston 58 are vertically aligned. At the top, the piston 58 carries a horizontally oriented piston plate 63, which has at the center a vertically oriented, conical recess 64 for receiving the tip 37 of the drive member 34.

The lower housing part 3 has at the top a pot-shaped closure cap 65 with a cylindrical or conical jacket. The bottom of the cap 65 is disposed above the piston plate 63 and has a central upper housing opening 67, through which the piston plate 63 is accessible from above. At the edge of your shell, the cap 65 has outwardly projecting protrusions 68 which are snapped into corresponding recesses 69 of the hollow cylindrical portion 47 of the housing base 3.

The bottom of the cap 65 limits the displacement of the piston 58 upwards. A trained as a spiral spring piston spring 70 which is supported at the bottom of the extension 55 and the top of the underside of the piston plate 63, biases the piston 58 against the underside of the cap 65 before.

Furthermore, the pipette 1 has a discharge device 71. The discharge device 71 comprises a discharge slide 72, which is arranged on the housing lower part 3. The discharge slide 72 has a contour adapted to the contours of the hollow cylindrical section 47, the upper hollow taper section 49 and the lower hollow taper section 49. Below it has an annular discharge end 73. The discharge end 73 is in the position of the discharge slide 72 of Fig. 1 pushed as far as possible up to the lower housing part 3, so that the conical projection 50 is free for attaching a pipette tip 51.

Above the discharge slide 72 is connected to a discharge extension 74. This includes three vertical discharge bars 75, which are connected to the upper edge of the discharge slide 72. The discharge bars 75 are evenly distributed over the upper edge of the discharge slide 72. The discharge bars 75 are connected at the bottom via a first snap connection with a discharge ring 76, which is connected via a second snap connection with the upper edge of the discharge slide 72. At a distance from the Abwurfring 76, the discharge rods 75 are connected at the top at its inner periphery by an annular upper Abwurffederlager 77 with each other. The upper Abwurffederlager 77 has an L-shaped cross section, wherein the horizontal leg of the cross section, the through hole 33 adjacent to the Überhubfederlagers 32. The vertical, circumferential leg of the upper Abwurffederlagers 77 is directed downward.

The discharge bars 75 have actuation ends 78 at the top.

The discharge extension 74 and the discharge bars 75 are hineinerstreckt through the lower housing opening 45 in the upper housing part 2. The displacement of the Abwurfverlängerung 74 upwards is limited by conditioning the upper Abwurffederlagers 77 on the underside of the Überhubfederlagers 32.

Below the upper Abwurffederlagers 77 are from the inside of the upper housing part 2 before three webs 79, which are arranged distributed uniformly over the inner circumference and pass through recesses of the lifting body 10. This is especially in FIG. 4 shown. The webs 79 form a lower Abwurffederlager 80. A designed as a helical spring ejection spring 81 is under bias between the upper Abwurffederlager 77 and the lower Abwurffederlager 80th arranged and pushes the ejector 71 upwards, so that the upper Abwurffederlager 77 abuts the overstroke spring bearing 32.

The lower housing part 3 is guided with an upper region of the hollow cylindrical section 47 into the lower housing opening 45 of the housing upper part 2. The means for releasably connecting 46, 54 of the lower housing part 3 and upper housing part 2 are detachably connected to each other. The drive member 34 engages with the tip 37 in the upper housing opening 67 and is located in the recess 64 on the piston head 63 at. The piston plate 63 pushes the drive member 34 upwards and via the decoupling device 44, the lifting rod 6 is pressed against the threaded spindle 8 with the collar.

According to Fig. 7 and 8th the lifting body 10 has a lower hollow cylindrical portion 82 and an upper hollow cylindrical portion 83, wherein the upper hollow cylindrical portion 83 has a smaller inner and outer diameter and is shorter than the lower hollow cylindrical portion 82. The upper edge of the lower hollow cylindrical portion 82 is connected to the bottom edge of the upper hollow cylindrical portion 83 connected by an annular disc-shaped shoulder 84.

From the lower edge of the lower hollow cylindrical portion 82 are three struts 85 of the lifting body 10 parallel to the central axis of the lower and upper hollow cylindrical sections 82, 83 downwards. In the area of the spring legs 85, the lifting body 10 generally has a greater wall thickness than in the region of the lower and upper hollow cylindrical sections 82, 83. In the vicinity of their lower ends, the spring legs 85 are provided on the outside respectively with recesses 86 for latching with corresponding elevations of the upper housing part 2 ,

The spindle nut 9 is substantially hollow cylindrical and inserted with a lower portion in the upper hollow cylindrical portion 83. The spindle nut 9 and the upper hollow cylindrical portion 83 are manufactured by two-component injection molding and are thereby also directly connected to each other.

As already mentioned, the threaded spindle 8 is screwed into the spindle nut 9 and the lifting rod 6 inserted into the upper passage 7 of the spindle nut 8.

The lift body 10 has a plurality of axially extending slots 89 in the lower hollow cylindrical portion 82. The slots 89 begin at a distance from the upper edge of the lower hollow cylindrical portion 82 and extend to the lower edge of the lower hollow cylindrical portion 82. In the example, four slots 89 are present which are uniformly distributed over the circumference of the lower hollow cylindrical portion 82.

In the lower hollow cylindrical portion 82 of the lower stopper body 27 is inserted. Four radial projections 29 of the lower stopper body 27 pass through the slots 89 and slightly project outwardly from the outer periphery of the lower hollow cylindrical portion 82.

The over-stroke spring bearing 32 has the shape of a disc with an upwardly projecting edge. The over-stroke spring bearing 32 is engaged with its outer edge in recesses 90 on the inside of the struts 85. The recesses 90 extend for manufacturing reasons from the inside to the outside of the struts 85th

The overstroke spring 31 is disposed between the lower stopper body 27 and the overstroke spring bearing 32 in the lower hollow cylindrical portion 82. It is biased so that it pushes the lower stopper body 27 upwards.

The lower hollow cylindrical portion 82 has an outer thread 91 at the outer periphery from the upper edge. The slots 89 extend into a lower portion of the outer thread 91.

A circular cylindrical threaded ring 92 with an internal thread 93 is screwed onto the external thread 91. The threaded ring 92 has at the top of an inwardly projecting, further annular disc-shaped shoulder 94, which is arranged above the shoulder 84. On the upper edge or on the further paragraph 94 is a toothing 95 with parallel to the screw axis of the internal thread 93 facing teeth available. The toothing 95 extends along a helix 96 about the helical axis of the internal thread 93, which has the same pitch as the external thread 91 and the internal thread 93. The toothing 95 is a bevel gear.

The stopper body 27 is pressed by the overstroke spring 31 with the projections 29 against the lower edge of the threaded ring 92.

The spindle nut 9 carries on the outer circumference of a bearing 97 in the form of a radially outwardly projecting pin, which projects into an opening 98 of the upper hollow cylindrical portion 83. The pin has on the outer circumference a circumferential detent groove 99. A drive gear 100 is mounted with a hollow shaft 101, which has a circumferential latching projection 102 on the inner circumference, on the bearing 97, so that the locking bead 102 engages in the locking groove 99. The drive gear 100 is rotatable on the bearing 97. The drive gear 100 meshes as a pinion with the teeth 95 of the screw ring 92. The drive gear 100 is formed as a bevel gear.

The drive gear 100 has on an outer end face a tool engagement 103 in the form of a hexagon socket.

On the outer circumference of the screw ring 92 markings 104 are arranged in the form of Arabic numerals. Starting from a central arranged digit 0 numbers 1 2 3 ... are arranged in ascending order in the various circumferential directions. The marks 104 are evenly distributed over the circumference.

The markings 104 are arranged on a further helical line 105 which has the same pitch as the external thread 91 and the internal thread 93 (cf. Fig. 9 ).

According to Fig. 1 and 2 the screw ring 92 is arranged in the upper housing part 2 below a window 106, so that in each case a marking 104 is visible from the outside. Furthermore, the drive gear 100 is arranged below a hole 107 in the housing upper part 2, so that a tool in the form of a hexagonal wrench can be inserted into the tool attachment 103 from the outside.

The pipette 1 can be used as follows:

It is gripped on the upper housing part 2. A metering stroke is adjusted by rotating the actuator 4 until the meter wheels 22 indicate the desired metering volume. When turning the actuating element 4, the threaded spindle 8 is rotated about the Spindelmitnehmer 10 and due to their Threaded connection axially displaced with the fixed in the upper housing part 2 spindle nut 9. At the same time, the transmission part 19 is turned over the further radial projections 15, 16 and the counter 23 is adjusted. As a result, the set axial position of the threaded spindle 8 in the upper housing part 2 and thus the metering volume at the counter 23 is read.

Further, a pipette tip 51 is clamped on the lug 50, preferably by being pressed into a pipette tip 51, which is held in a holder.

Before sucking liquid, air is expelled from the cylinder 57 by pushing the piston 58 downward by means of the operating member 4 until the further collar 38 strikes the lower stopper body 27. Here, the lifting rod 6 moves via the decoupling device 44, the drive element 34 down and the piston 58 is pushed deeper into the cylinder 57. Due to the force between the magnet 40 and the armature 39, the decoupling device 44 does not decouple.

Thereafter, by means of the pipette 1, the lower end of the pipette tip 51 is immersed in the liquid and the desired amount is sucked into the pipette tip 51 by releasing the actuating element 4. Here, the piston spring 70 pushes the piston 58 and thus the drive element 34 and the lifting rod 6 back to the starting position, in which the collar 25 rests against the threaded spindle 8.

In this situation, the pipette is 1 in Fig. 1 . 2 . 5 . 6 and 10a shown.

Thereafter, the pipette tip 51 can be aligned with the lower end to another vessel by means of the pipette 1. By pressing the actuator 4 down the lifting rod 6 is moved down and the decoupling device 44, the drive element 34 is displaced downwards, so that the piston 58 is again moved in the cylinder 57 down. In this case, the set metering is essentially delivered. This situation is in Fig. 10b shown.

Remains remaining in the pipette tip 51 can be blown out by pressing the actuating element 4 further down under increased force. Here, the lower stopper body 27 is displaced against the action of the overstroke spring 31 in the guide slots 30 down and on the decoupling device 44, the drive element 34 further displaced downwards, which pushes the piston 58 even deeper into the cylinder 57. During the overstroke, a further overpressure is generated which pushes out residual liquid adhering to the inner wall of the pipette tip 51.

The overstroke is completed when the drive element 34 with the other collar 38 strikes the overstroke spring bearing 32, which forms the end stop. At the same time, the projections 29 reach the actuating end 78 of the discharge extension 74 or are located at a very small distance above it. This situation is in Fig. 10c shown.

Thereafter, the pipette tip 51 can be dropped. For this purpose, the actuator 4 is pressed with increased force further down. The over-stroke spring bearing 32 prevents the drive member 34 from moving further down. Due to the increased force, the magnet 40 releases from the armature 39 and the lifting rod 6 moves further down and takes the lower Stop body 27 with. The lower stopper body 27 presses with the projections 29, the discharge extension 74 to the operating ends 78 down. The Abwurfverlängerung 74 takes the discharge slide 72 with downward, which pushes the pipette tip 51 from the approach 50 with the discharge end 73.

During the discharge stroke, the piston 58 is not further moved in the cylinder 57 down. As a result, no dead volume is needed at the bottom of the cylinder 57, and the piston 58 does not hit the bottom of the cylinder 57. If the magnet 40 is released from the armature 39, the force required for the further displacement of the actuating element 4 down again is reduced. The discharge stroke is completed when the Abwurfverlängerung 74 meets a discharge stop, not shown in the housing. This situation is in Fig. 10d shown.

After releasing the actuator 4, the pipette 1 automatically returns to the initial situation of Fig. 1 . 2 . 5 . 6 and 10a back. Here, the ejection spring 108 presses the discharge extension 74 and thus the discharge slide 72 upwards. Further, the decoupling spring 43 pushes the lifting rod 6 with the magnet 40 upwards until the magnet 40 is held by the magnetic forces on the armature 39. Further, the overstroke spring 31 pushes the lower stopper body 27 upward until the projections 29 have arrived at the upper ends of the guide slots 30. Further, the piston spring pushes the piston 58, the drive element 34 and the decoupling device 44, the lifting rod 6 upwards until the collar 25 rests against the threaded spindle 8.

In a further variant, the decoupling unit 44, 43 can be dispensed with in order to execute the stroke, overstroke and discharge stroke. The lifting rod 6 acts directly on the conical recess 64 of the piston 58.

The upper housing part 2 can be easily connected to another housing lower part 3 to a housing in which the cylinder 57 and the piston 58 have a different cross-section. Accordingly, the same upper housing part 2 can be used for the production of pipettes 1 with different dosing volumes. Furthermore, it is possible, in the event of a defect, to easily exchange the lower housing part 3 or upper housing part 2 or, if required, to fit the upper housing part 2 with another lower housing part 3. In addition, the housing lower part 3 can be easily removed from the upper housing part 2 for maintenance, repair and cleaning purposes.

The pipette 1 has a factory calibration, i. it is calibrated by the manufacturer of the pipette 1. For this purpose, the settings of the counter 23 and the threaded spindle 8 are matched. In this tuning, the screw ring 92 is set so that the numeral 0 is visible through the window 106.

The user can perform a user calibration by turning the drive gear 100 in one direction or the other by means of a polygonal key. Here, the threaded ring 92 is axially displaced on the external thread 91. Accordingly, the lower stopper body 27, which is pressed by the overstroke spring 31 against the lower edge of the screw ring 92, also axially displaced. This changes the stroke that the lifting rod 6 performs when the collar 25 is displaced from the threaded spindle 8 to the lower stop member 27. An axially directed projection 108 adjacent to the uppermost tooth of the axially directed gear 95 prevents the drive gear 100 from disengaging the gear 95 ( Fig. 9 ).

For setting the screw ring 9 tables can be made available to the user, depending on the ambient conditions (pressure, temperature) and the properties of the liquid to be pipetted (density, viscosity, surface tension) specify the to be set in the window 106 markers 104. Alternatively, the user himself can determine suitable settings by means of measurements and adjust them during user calibration.

The factory calibration is easily retrievable by rotating the threaded ring 92 so that the zero is visible in the window 106.

List of reference numbers used

1

pipette

2

Housing top

3

Housing bottom

4

actuator

5

Cover of the actuating element

6

cylindrical lifting rod

7

Upper passageway

8th

screw

9

spindle nut

10

lifting body

11

Spindelmitnehmer

12

hexagon

13

hole

14

Allen

15, 16

radial projections

17, 18

groove

19

transmission part

20

sprocket

21

Zählwerksgetriebe

22

Zählwerksräder

23

counter

24

housing cover

25

beaded waistband

26

lower front side

27

lower stop body

28

lower passageway

29

projections

30

guide slots

31

travel spring

32

Überhubfederlager

33

Through-hole

34

driving element

35

upper sleeve section

36

lower sleeve section

37

frustoconical tip

38

another bunch

39

hollow cylindrical anchor

40

hollow cylindrical magnet

41

pot

42

needle-shaped section

43

decoupling spring

44

decoupling device

45

lower housing opening

46

Means for detachable connection

47

hollow cylindrical section

48

upper hollow cone section

49

lower hollow cone section

50

conical approach

51

pipette tip

52

upper opening

53

lower opening

54

further means for detachable connection

55

extension

56

connecting channel

57

cylinder

58

piston

59

O-ring

60

piston seal

61

needle-shaped extension

62

Through opening

63

piston plate

64

conical depression

65

cup-shaped cap

67

upper housing opening

68

projections

69

deepening

70

piston spring

71

discarding equipment

72

ejection slide

73

discharge end

74

shedding extension

75

Abwurfstange

76

shedding ring

77

Upper ejection spring bearing

78

actuating end

79

web

80

Lower ejection spring bearing

81

ejection spring

82

lower hollow cylindrical section

83

Upper hollow cylindrical section

84

annular disc-shaped heel

85

strut

86

deepening

87

locking element

88

locking element

89

slot

90

recess

91

external thread

92

screw ring

93

inner thread

94

another annular disc-shaped paragraph

95

gearing

96

helix

97

camp

98

breakthrough

99

locking groove

100

drive gear

101

wave

102

latching bead

103

tool application

104

marks

105

additional helix

106

window

107

hole

108

axial projection

Claims (15)

1. A pipette with

   - a rod-like housing (2, 3),

   - a seat (50) for releasably holding a pipette tip (51) on the bottom end of the housing (2, 3),

   - a displacement device comprising a displacement chamber (57) with a displaceable boundary (58),

   - a connection channel (56) connecting the displacement chamber (57) with an opening in the seat,

   - a drive device coupled with the displaceable boundary (58) having an axially displaceable lift rod (6) for displacing the displaceable boundary (58) of the displacement chamber (57),

   - an upper stop body, a lower stop body (27) and a stop element (25) on the periphery of the lift rod (6) for delimiting the lift of the lift rod (6),

   - an overlift spring (31), via which the lower stop body (27) is reinforced against a displacement downwards at an overlift spring seat (32),

   - a screw element (10) permanently connected with the housing (2, 3) and a screw element (92) engaging with it and displaceable in the housing, which is coupled with the lower stop body (27) in order to displace it during a displacement of the displaceable screw element in the axial direction of the lift rod (6)

   - characterized by

   - a toothing (95) progressing along a screw line (96) with the same slope as the thread (93) of the displaceable screw element (92) with teeth directed in the direction of the screw axis of the displaceable screw element (92) on the upper edge of the displaceable screw element (92),

   - a driving tooth wheel (100) rotatably mounted on a bearing (97) permanently connected with the housing (2, 3), which cogs with the toothing (95) of the displaceable screw element (92) and

   - means (103) for turning the driving tooth wheel (100).
2. The pipette according to claim 1, in which the displaceable screw element (92) is a threaded ring arranged concentrically to the lift rod with a thread (93) on the periphery, which has the tooth (95) on top and rests on the lower stop body (27) on the bottom.
3. The pipette according to claim 2, in which the fixed screw element (10) is a hollow, cylindrical lift body, which has an external thread (91) on the outer periphery, with which an internal thread (93) engages on the inner periphery of the threaded ring (92), the lift body (10) has several axially extended slits (89), the lower stop body (27) has several projections (29) protruding outwards, which pierce the slits (89) and have sections protruding out of the lift body (10), on which the threaded ring (92) sits.
4. The pipette according to claim 3, in the case of which the overlift spring seat (32) is arranged in the lift body (10) and the overlift spring (31) is arranged between the lower stop body (27) and the overlift spring seat (32) in the lift body (10).
5. The pipette according to one of claims 1 to 4, in the case of which the upper stop body (8) is a threaded spindle, which is screwed into a spindle nut (9) permanently connected with the housing (2, 3) and which has an upper passage channel (7), through which the lift rod (6) passes and/or the lower stop body (27) is circular-disk-shaped and has a lower passage channel (28), through which the lift rod (6) extends.
6. The pipette according to claim 5, in which the lift body (10) is permanently connected on top with the spindle nut (9).
7. The pipette according to one of claims 3 to 6, in the case of which the bearing (97) of the driving tooth wheel (100) above the outer thread (91) is permanently connected with the lift body (10).
8. The pipette according to one of claims 1 to 7, in the case of which the lift body (10) is connected with the housing via a snap connection.
9. The pipette according to one of claims 1 to 8, in the case of which the driving tooth wheel (100) and the displaceable screw element (92) are bevel wheels or crown wheels.
10. The pipette according to one of claims 1 to 9, which has a display device (104, 106) for displaying the position of the lower stop body (27).
11. The pipette according to claim 10, in the case of which the threaded ring (92) has spaced markings (104) on the outer periphery in the circumferential direction and the housing has a window (106) for reading a marking (104) arranged below the window (106).
12. The pipette according to claim 11, in the case of which the markings (104) are arranged on the periphery of the threaded ring (92) on a further screw line (105), the slop of which matches the slope of the thread (93) of the displaceable screw element (92).
13. The pipette according to one of claims 1 to 12, in the case of which the driving tooth wheel (100) has a tool drive (103) for turning the driving tooth wheel and the housing has a hole (107), through which the tool drive (103) is accessible by means of a tool inserted into the hole (107) from the outside.
14. The pipette according to one of claims 1 to 13, which has means for delimiting (108) the turning of the displaceable screw element (92) so that the highest tooth of the toothing (95) is not released from the driving tooth wheel (100).
15. The pipette according to one of claims 1 to 14, in the case of which the toothing (95) of the displacement screw element (92) is delimited by an axial projection (108) in addition to the highest tooth, which blocks the driving tooth wheel (100) at the end of the axial toothing (95).

Images