PIPETTE WITH ADJUSTABLE DOSING VOLUME

Description

[0001] The invention relates to a pipette with adjustable dosing volume.

[0002] Pipettes are used primarily in laboratories for dispensing liquids. For this purpose, the upper end of a pipette tip is clamped onto a seat on the pipette. The seat is usually a conical or cylindrical projection on the pipette body, onto which a pipette tip can be clamped via an upper opening in its tubular body. The pipette tip can aspirate and dispense liquid through a lower opening in its tubular body. Air-cushion pipettes comprise a displacement device for air, which communicates with the pipette tip through an opening in the seat. The displacement device displaces an air cushion, so that liquid is sucked into and expelled from the pipette tip. For this purpose, the displacement device has a displacement chamber with a displaceable displacement element.The displacement device is usually a cylinder with a movable piston inside it.

[0003] After use, the pipette tip is removed from its seat and replaced with a fresh one. This prevents contamination from liquid transfer during subsequent dispensing. Pipettes usually have an ejector mechanism that allows the tip to be ejected by pressing a button without touching the tip. Single-use pipette tips are usually made of plastic.

[0004] The piston is coupled to a drive mechanism that moves the piston within the cylinder. The drive mechanism has a lifting rod that can be moved between an upper and a lower stop by means of a stop element. When air is first drawn into the cylinder, the stop element is at the lower stop. When air is first expelled from the cylinder, the stop element is at the upper stop. The amount of fluid drawn in or discharged depends on the stroke of the lifting rod between the lower and upper stops.

[0005] In fixed-volume pipettes, the distance between the upper and lower stops is constant. In pipettes with adjustable dispensing volumes, the position of the upper stop is variable. Common pipettes have an upper stop on the underside of a threaded spindle, which is adjustable using a spindle nut fixed in the housing. Adjustment devices are provided for adjusting the threaded spindle. These are coupled to display devices that indicate the set dispensing volume in the form of a counter.

[0006] DE 43 35 863 C1, EP 0 649 678 B1 and US 5,531,131 describe a pipette in which an actuating button protrudes from the top of the housing and is connected to the upper end of a lifting rod, which is connected to the piston at the lower end. The lifting rod passes through passages of a threaded spindle and a lower stop. It has a stop element in the form of an outwardly projecting bead that limits the movement of the lifting rod between the upper stop at the bottom of the threaded spindle and the lower stop. By pressing in the actuating element against the force of a return spring, the piston is moved deeper into the cylinder until the stop element rests against the lower stop. After the actuating element is relieved of pressure, the piston returns to its initial position due to the effect of the return spring, in which the stop element rests against the threaded spindle.Adjustment devices for adjusting the threaded spindle have a rotatably mounted adjustment sleeve in the housing, which protrudes from the top of the housing and in which the actuating button can be axially moved. The adjustment sleeve is connected to the threaded spindle in a rotationally fixed manner via axial grooves on its inner circumference and drivers projecting radially from the upper end of the threaded spindle. By turning the adjustment sleeve, the threaded spindle can be adjusted to the upper stop and thus the dispensing volume. The adjustment sleeve has a spur gear at its lower end, which is positively coupled to a spur gear of a counter via coupling devices with two coupling spur gears on a common axis. The axis on which the two coupling spur gears are mounted can be moved using switching devices in order to release the coupling devices. This enables factory calibration of the pipette.The disadvantage is that the calibration requires an iterative procedure, since the adjustment of the upper stop by turning the upper end of the adjustment sleeve without measuring the respective set stroke is inaccurate.

[0007] The aforementioned documents describe a previously known factory calibration in which a slip clutch between the piston stroke adjustment devices and a counter is adjusted. For this purpose, an opening is provided in the pipette housing through which a screwdriver can be inserted onto a slip clutch consisting of a bevel gear set. By holding the volume setting and turning the screwdriver, or vice versa, the coupling between the volume setting and the counter can be changed. The accuracy deviation achieved in this way (difference between aspirated and displayed liquid volume) can be checked by weighing a pipetted mass. A disadvantage is stated that this adjustment of the pipette correction factor is not particularly easily accessible from the outside and is usually only used for factory adjustment or by the customer in exceptional cases.Another disadvantage is that when the counter is adjusted, a frictional engagement element of the slip clutch is constantly moving, making it necessary to secure the lifting system to prevent it from being adjusted. Furthermore, the constant frictional contact of the frictional engagement elements leads to considerable wear in the system.

[0008] DE 10 2005 033 378, EP 1 743 701 B1, and US Pat. No. 8,133,453 B4 B2 describe a pipette of the type described above, which additionally has an adjustment device for adjusting the position of a holder holding the lower stop relative to the cylinder and a display device for displaying the position of the holder. This makes it easier for the user to change the calibration and retrieve the factory calibration.

[0009] DE 10 2012 003 846 B and EP 2 633 915 B1 describe a pipette in which the adjustment device for adjusting the position of the lower stop has a construction which, compared to the previously described pipette, requires fewer components, thereby enabling the user to calibrate with better calibration accuracy.

[0010] DE 10 2016 121 814 A1 describes a pipette that has an adjustment device for setting the dispensing volume, a display device for displaying a set dispensing volume, and a detachable coupling. The detachable coupling serves to separate the adjustment device and the display device. After separation, the adjustment device and display device can be adjusted separately. Separation occurs via the actuation of a radially acting reset element. The reset element acts on a toothing that, when coupled, connects the concentrically arranged adjustment device and display device. Subsequently, the dispensing volume and the display device display can be adjusted separately to perform calibration.The disadvantage is that calibration can easily be falsified accidentally, through ignorance or manipulation, and therefore critical deviations are not unlikely under laboratory conditions.

[0011] DE 203 25 525 C1 describes a pipette that has a setting device for setting the dispensing volume, a display device for displaying a set dispensing volume, and coupling devices. The coupling devices ensure that, when disengaged, operating the setting device no longer results in a change in the dispensing volume. The setting device and the display device remain connected, so that operating the setting device results in a change in the displayed dispensing volume. Calibration is achieved by adjusting the display device compared to a measurement of the actual dispensing volume. A disadvantage is that separate setting of the dispensing volume and the display setting is not possible.

[0012] EP 2 470 302 EP B1 describes a pipette which has an adjustment device for setting the dosing volume, a display device for displaying a set dosing volume and a positive coupling device. The coupling device serves to separate the adjustment device and the display device. After separation, the adjustment device and display device can be adjusted separately. A coupling tool is used to operate the coupling. The same coupling tool is inserted with a different side at a different location to change the display of the display device. For calibration, the display of the display device is adjusted to the actually measured dosing volume. A disadvantage is the complicated handling of the coupling tool, which has to be inserted in different locations.

[0013] Based on this, the object of the invention is to create a pipette that facilitates calibration.

[0014] The problem is solved by a pipette having the features of claim 1. Advantageous embodiments of the pipette are specified in subclaims.

[0015] The pipette with adjustable dosing volume according to the invention comprises: a rod-shaped housing, at least one seat for releasably holding a pipette tip at the lower end of the housing, a displacement device comprising a displacement chamber with a displacement element displaceable therein, a connecting channel connecting the displacement chamber to an opening in the seat, a lifting rod coupled to the lower end of the displacement element and displaceable longitudinally in the housing for displacing the displacement element in the displacement chamber, an operating knob connected to the upper end of the lifting rod and protruding from the housing, a stop element on the outer circumference of the lifting rod, an upper stop for the stop element and a lower stop for the stop element to limit the stroke of the lifting rod, an adjustment device for adjusting the position of the upper stop in the housing, a display device for displaying a set dosing volume,a positive coupling device between the setting device and the display device, which is designed to couple the setting device to the display device in a coupled state and to uncouple the setting device from the display device in a uncoupled state, an adjustment device which is designed to change the setting of the display device when the coupling device is uncoupled, characterized in thatthe coupling device is designed such that it can be uncoupled and coupled into the housing by inserting an adjusting tool from the outside of the housing, the adjusting device is designed such that when the coupling device is uncoupled, the setting of the display device can be changed from the outside of the housing by means of an adjusting tool and the same adjusting tool can be inserted into the housing through the same housing opening to uncouple the setting device from the display device and to change the setting of the display device.

[0016] With the pipette according to the invention, calibration (adjustment) in the factory, by the service department and by the customer is made considerably easier. This is achieved by the fact that the display device can be adjusted when the positive coupling device is disengaged, without changing the stroke of the stroke rod set using the adjustment device. By disengaging the positive coupling device, the adjustment device is separated from the display device, so that adjusting the display device using the adjustment device does not change the position of the upper stop. Because the coupling device between the adjustment device and the adjustment device is a positive coupling device, it is ensured that when the coupling is disengaged, an adjustment of the display device cannot be transferred to the upper stop. For this purpose, it is not necessary to remove the upper stop orto fix the lifting system through additional measures such as holding or blocking it using a tool inserted from the outside. Furthermore, there is no wear in the coupling device when adjusting the indicator. Adjustment is facilitated by the fact that the indicator can be set directly to the result of a gravimetric measurement, thereby achieving significant time savings compared to an iterative approach. Furthermore, the invention enables the indicator and the position of the upper stop to be adjusted independently of each other. For this purpose, the indicator can be adjusted with the coupling device disengaged, and the position of the upper stop can be adjusted independently using the adjustment device.

[0017] According to one embodiment of the invention, the coupling device is designed so that it can be coupled and uncoupled from the outside of the housing. This allows the pipette to be calibrated without opening or disassembling it.

[0018] The coupling device is designed such that it can be uncoupled and coupled into the housing from the outside by inserting an adjustment tool into the housing. The use of an adjustment tool makes it easier to uncouple and couple the coupling device and prevents unintentional uncoupling and coupling. The pipette comprises an adjustment device which is designed to change the setting of the display device when the coupling device is uncoupled. The adjustment device can make it easier to adjust the display device. For this purpose, the adjustment device is designed such that the setting of the display device can be changed from the outside of the housing. The adjustment device is designed such that when the coupling device is uncoupled, the setting of the display device can be changed from the outside of the housing using an adjustment tool.This facilitates the adjustment of the indicator and prevents accidental adjustment. The coupling device and the adjustment device are designed so that the adjustment device can be coupled and uncoupled from the indicator and the setting of the indicator can be changed using the same adjustment tool. For this purpose, the same adjustment tool can be inserted into the housing from the outside of the housing through the same housing opening.

[0019] According to a further embodiment, the coupling device and adjustment device are designed such that the coupling device can first be uncoupled by inserting an adjustment tool into the housing. The setting of the display device can be changed by subsequently inserting the adjustment tool deeper into the housing and then rotating the adjustment tool. This further facilitates pipette calibration.

[0020] According to a further embodiment, the positive coupling device is a tooth coupling or a claw coupling.

[0021] According to a further embodiment, the positive coupling device comprises a driving first gearwheel coupled to the adjustment device and mounted rotatably about a rotational axis, an axle mounted in a first bearing in the housing and supporting the first gearwheel for translational displacement in the direction of the rotational axis, a driven second gearwheel of the display device meshing with the first gearwheel, a cam mechanism with a first gear element carried by the axle and a second gear element arranged in a fixed position in the housing, and a rotary lever connected in a rotationally fixed manner to the first gear element, wherein the first gearwheel is held on the axle and prevented from being displaced upwards on the axle and the first gear element is prevented from being displaced downwards on the axle, and by pivoting the rotary lever, the axle can be displaced translationally via the cam mechanism and the first gearwheel can be disengaged from the second gearwheel.to decouple the setting device from the display device. This design combines reliable function with ease of use.

[0022] According to a further embodiment, the axle has a shoulder and / or a groove at the ends with a locking ring releasably held therein, and the first gear is prevented from moving upwards on the axle by a shoulder or a groove with a locking ring held therein, and the first gear element is prevented from moving downwards by a further shoulder or a further groove with a further locking ring held therein. According to a further embodiment, the axle is a rotatably mounted shaft, and either the first gear is connected to the shaft in a rotationally fixed manner (non-rotatably), and the first gear element and the rotary lever connected to it in a rotationally fixed manner are rotatably mounted on the shaft, or the first gear is rotatably mounted on the shaft, and the first gear element and the rotary lever are connected to the shaft in a rotationally fixed manner. According to a further embodiment, the rotary lever is accessible from the outside of the housing.The rotary lever can be pivoted, in particular, by means of an adjustment tool or manually. According to another embodiment, the rotary lever can be pivoted by inserting the adjustment tool into an opening in the housing.

[0023] According to another embodiment, the first gear element is a first cam and / or the second gear element is a second cam. In an alternative embodiment, only one of the two gear elements is a cam, and the other gear element is a scanning element that scans the cam.

[0024] According to a further embodiment, a first spring device is arranged between the axle and an abutment arranged in a fixed position in the housing. The first spring device presses the axle with the first gear into a position in which it meshes with the second gear, and the first gear can be disengaged from the second gear counter to the action of the first spring device. Preferably, the first spring device is preloaded when the first gear meshes with the second gear. In this embodiment, when the coupling device is uncoupled, the first spring device is (further) preloaded so that when the rotary lever is relieved, the first spring device presses the axle into the position in which the first gear meshes with the second gear. The coupling device is thus automatically re-engaged after the rotary lever is relieved, which further facilitates operation.

[0025] According to a further embodiment, the adjustment device comprises a driving first wheel which is rotatable about a rotational axis and translationally displaceable in the direction of the rotational axis and is mounted in a second bearing in the housing. The driving first wheel can be translationally displaced until it rests against a driven second wheel coupled to the display device, in order to rotate the second wheel and change the setting of the display device by rotating the first wheel. This facilitates the adjustment of the display device. According to a further embodiment, the rotational axis of the first wheel is aligned perpendicular to the rotational axis of the second wheel. According to a further embodiment, the first wheel can be translationally displaced and rotated from the outside of the housing. This embodiment is particularly suitable for combination with the above-mentioned positive coupling device, which comprises a rotary lever accessible from the outside of the housing.

[0026] According to a further embodiment, the first wheel can be displaced up to the second wheel by means of an adjustment tool attached thereto, and the first wheel can be rotated by rotating the adjustment tool inserted into a tool engagement of the first wheel and the second wheel can be rotated by the first wheel.

[0027] According to a further embodiment, the first wheel and the second wheel are friction wheels of a friction gear. According to another embodiment, the first wheel and the second wheel are gears, for example, bevel gears with rotational axes aligned perpendicular to each other.

[0028] According to a further embodiment, the first spring device, via the axle and the unloaded rotary lever, pushes the first wheel away from the second wheel until it rests against the second bearing. As a result, when the rotary lever is unloaded, the first wheel is automatically moved into a position where it is not in contact with the first wheel.

[0029] According to another embodiment, a second spring device is arranged between the first wheel and a second abutment arranged in a fixed position in the housing. The second spring device presses the first wheel away from the second wheel and the first wheel can be displaced against the action of the second spring device until it rests on the second wheel. According to a further embodiment, the second spring device is preloaded when the first wheel is pressed away from the second wheel until it rests on a stop element. By displacing the first wheel until it rests on the second wheel, the second spring device is (further) preloaded so that the first wheel automatically returns to its starting position in contact with the stop element after the load is removed. This further simplifies operation.

[0030] According to a further embodiment, the coupling device and the adjustment device are designed for actuation by means of an adjustment tool which has a shaft with a profile adapted to the tool engagement of the first wheel and a handle connected to the shaft in a rotationally fixed manner, in order to pivot the rotary lever by inserting the shaft into the opening of the housing, to establish a rotationally fixed connection with the first wheel, to bring the first wheel into frictional connection with the second wheel by further inserting the shaft and to rotate the second wheel by rotating the adjustment tool by means of the first wheel.

[0031] Another design features an overtravel spring, which supports the lower stop against downward displacement by the stop element on the outer circumference of the stroke rod, against an overtravel spring bearing fixed in the housing. This enables an overtravel for blowing out residual sample liquid from the pipette tip by means of the displacement device.

[0032] According to a further embodiment, the pipette has a threaded spindle, at the lower end of which the upper stop is formed and which has a passage through which the lifting rod passes. By arranging a threaded spindle with the upper stop at the lower end in a spindle nut, an adjustable upper stop is realized.

[0033] According to a further embodiment, the adjustment device comprises an adjustment sleeve rotatably mounted in the housing, with an adjustment element accessible from the outside of the housing, which is coupled to the upper stop via a gear. According to a further embodiment, the gear comprises axially extending grooves on the inner circumference of the adjustment sleeve, into which radial projections at the upper end of the threaded spindle engage. This enables easy adjustment of the threaded spindle by turning an end of the adjustment sleeve protruding from the housing.

[0034] According to a preferred embodiment, the display device is a (roller) counter.

[0035] Embodiments of such overtravel devices, threaded spindles with spindle nuts, adjustment devices, and display devices are described in EP 0 649 678 B1, EP 1 743 701 B1, and EP 2 633 915 B1. In this regard, reference is made to EP 0 649 678 B1, EP 1 743 701 B1, and EP 2 633 915 B1.

[0036] Finally, the invention relates to a set comprising a pipette according to one of claims 1-11 or one of the previously described further embodiments and an adjustment tool, wherein the adjustment tool has a shaft with a profile adapted to the tool engagement of the first wheel and a handle connected to the shaft in a rotationally fixed manner, in order to pivot the rotary lever by inserting the shaft into an opening in the housing, to establish a rotationally fixed connection with the driving first wheel, to bring the first wheel into frictional connection with the second wheel by further inserting the shaft and to rotate the second wheel by rotating the adjustment tool by means of the first wheel.

[0037] The invention is explained in more detail below with reference to the accompanying drawings of an exemplary embodiment. In the drawings: Fig. 1 shows a pipette according to the invention in a longitudinal section from the left side; Fig. 2 shows the same pipette in a longitudinal section from the right side; Figs. 3.1 to 3.4 show an adjustment mechanism of the same pipette in an enlarged side view from the right side ( Fig. 3.1 ), in a front view ( Fig. 3.2 ), in a side view from the left side ( Fig. 3.3 ) and in a rear view ( Fig. 3.4 ); Fig. 4.1 to 4.4 the same adjustment mechanism switched to a different switching stage enlarged in a side view from the right side ( Fig. 4.1 ), in a front view ( Fig. 4.2 ), in a side view from the left side ( Fig. 4.3 ) and in a rear view ( Fig. 4.4 ); Fig. 5.1 to 5.4 the same adjustment mechanism exploded in a side view from the right side ( Fig. 5.1 ), in a front view ( Fig. 5.2 ), in a side view from the left side ( Fig. 5.3 ) and in a rear view ( Fig. 5.4); Fig. 6 an assembly with a coupling device, an adjustment device and a counter in a side view; Fig. 7 a cam gear of the same arrangement in a perspective view obliquely from below and from the side; Fig. 8 the same arrangement with an adjustment tool arranged in front of it in a bottom view; Fig. 9 the same arrangement with the adjustment tool partially inserted for uncoupling the coupling device in a bottom view; Fig. 10 the same arrangement in the same situation in a front view; Fig. 11 the same arrangement with the adjustment tool fully inserted for adjusting the counter in a bottom view; Fig. 12 the same arrangement in the same situation in a perspective view obliquely from above.

[0038] In this application, the terms "top" and "bottom," "above" and "below," "top view" and "bottom view," and derivative terms such as "bottom" and "top," and "horizontal" and "vertical" refer to an orientation of the pipette in which the housing with the seat is oriented vertically downward. In this orientation, a pipette tip mounted on the seat can be directed toward a vessel below to aspirate or dispense liquid.

[0039] According to Fig. 1 and 2A pipette 1 according to the invention has a rod-shaped housing 2 with a lower housing part 3 and a housing upper part 4. The lower housing part 3 has a tubular base body 5 with a conical bottom at the top, from which a slender tubular, slightly conical extension 6 projects downwards, which has a seat 7 at the lower end for attaching a pipette tip 8. In the extension 6, a displacement chamber 9 in the form of a cylinder is formed, which is connected via a connecting channel 10 to an opening 11 in the underside of the seat 7.

[0040] The lower housing part 3 further comprises a displacement element 12 in the form of a piston of the displacement device, which is guided into the cylinder 11 via a sealing system 13 on the upper side of the base. The displacement element 12 has a plate 14 at its upper end, which has a dome-shaped recess centrally on the upper side. A first spring device 15 in the form of a helical spring is arranged between the plate 14 and the upper side of the base. The first spring device 15 presses the plate 14 from below against a closure cap 16, which is connected to the base body 5 and has a passage in the center through which the plate 14 is accessible from above.

[0041] The upper housing section 4 contains a lifting rod 17, which rests against the upper side of the plate 14. The lower end of the lifting rod 17 engages in the recess of the plate 14. A control knob 18 is fixed to the top of the lifting rod 17 and protrudes outward from the upper end of the housing 2.

[0042] The lifting rod 17 passes through a central spindle bore 19 of a threaded spindle 20 located in the upper housing section 4. The threaded spindle 20 has an external thread 21 that can be screwed into an internal thread 22 of a lifting body 23, which is held at the bottom on a first support 24 in the upper housing section 4. The lifting body 23 forms a spindle nut.

[0043] The lower end face of the threaded spindle 20 is an upper stop 25 for a stop element 26 in the form of an annular bead on the outer circumference of the lifting rod 17.

[0044] The threaded spindle 20 is connected at the upper end in a rotationally fixed manner to a driver 27, which is supported by means of radially outwardly projecting ribs 28 (cf. Fig. 5 ) engages in axial grooves 29 of a driving sleeve 30. The driving sleeve 30 is arranged concentrically to the threaded spindle 20 and is rotatably mounted on the outer circumference of the lifting body 23. The driving sleeve 30 has a circumferential first toothing 31 on the lower edge of the outer circumference. This is particularly evident in the Fig. 3 to 5 shown.

[0045] An adjusting sleeve 32 is slid onto the drive sleeve 30. The adjusting sleeve 32 is rotatably mounted on the outer circumference of the drive sleeve 30 and is guided axially displaceably between two limits on the drive sleeve 30. The upper end of the adjusting sleeve 32 protrudes outward from the upper end of the housing 2. There, the adjusting sleeve 32 has an adjusting ring 33 on its outer circumference, which has a knurling on the outer circumference.

[0046] The adjusting sleeve 32 has a second toothing 34 running around the outer circumference at the lower edge and a third toothing 35 running around the outer circumference slightly further up. The first toothing 31 and the second toothing 34 have the same diameter and the same number of teeth. The third toothing 35 has a larger diameter and a greater number of teeth than the second toothing 34.

[0047] The second toothing 34 is on the top side, and the third toothing 35 is closed on the bottom side by an intermediate disc 36. The bottom side of the disc 36 forms a lower limit 37, and the top side of the disc 36 forms an upper limit 38 for the displacement of the adjusting sleeve 32.

[0048] In addition to the drive sleeve 30 and the adjusting sleeve 32, a transmission shaft 39 is rotatably mounted on the first carrier 24. The transmission shaft 39 is provided with a fourth toothing 40 at the bottom, a fifth toothing 41 above it, and a sixth toothing 42 above it. The fourth toothing 40 and the fifth toothing 41 have the same diameter and the same number of teeth and are combined into a single toothing 43. The sixth toothing 42 is arranged at a distance from the fifth toothing 41. It has a smaller diameter and a lower number of teeth than the fifth toothing 41.

[0049] The transmitter shaft 39 is rotatably mounted at the top in a second carrier 44, which is fixed in the upper housing part 4.

[0050] In addition, a counter 45 in the form of a roller counter is held between the first carrier 24 and the second carrier 44. A counting roller axle 46 of the roller counter is mounted at the bottom in the first carrier 24 and at the top in the second carrier 44. The second carrier 44 is supported at the top on a projection in the housing. In addition, a drive gear 47 is rotatably mounted on an axle on the first carrier 24, which drive gear comprises two spur gears 48, 49 with different diameters that are connected to one another in a rotationally fixed manner. The spur gear 48 with the smaller diameter meshes with the first toothing 31 of the driver sleeve 30 and the

[0051] Spur gear 49 with the larger diameter meshes with a drive pinion 50 on an initial roller of the roller counter.

[0052] The spur gear 49 and the axle are components of a positive coupling device, which is explained further below.

[0053] The number rollers 51 of the counter 45 are visible from the outside of the housing 2 through a window 52 in the upper housing part 4, which has a transparent cover 53 (cf. Fig. 2 ).

[0054] A cup-shaped holder 54 is arranged in the upper housing section 4 below the lifting body 23. The holder 54 has an external thread 55, which is screwed into an internal thread 56 of a third support 57 fastened in the housing 2.

[0055] The holder 54 includes a cap-shaped lower stop 58, which is held under a downwardly curved upper edge 59 of the holder 54. An overtravel spring 60 in the form of a helical spring, which is supported on the bottom 61 of the holder 54, presses the lower stop 58 against the upper edge 59. The lifting rod 17 is guided through central passages of the lower stop 58, through the overtravel spring 60, and through a central passage in the bottom 61 of the holder 54.

[0056] The adjusting sleeve 32 is a drive shaft, the driving sleeve 30 is an output shaft and the transmission shaft 39 is a countershaft of a gearbox 63 designed as a spur gear 62. Switching between the different gear stages is carried out by axially displacing the adjusting sleeve 32 in a Fig. 3 and 4 shown lower switching position (fine adjustment position) and into a Fig. 4 shown upper switching position (quick adjustment position). In the fine adjustment position of Fig. 3The adjusting sleeve 32 is displaced downwards until the lower limit 37 rests on the upper side of the fifth toothing 41, and in the quick-adjustment position, the adjusting sleeve 32 is displaced upwards until the upper limit 38 rests on the underside of the sixth toothing 42. Thus, the adjusting sleeve 32 is simultaneously a switching device 64 of the manual transmission, with the adjusting ring 33 being a switching element 65 of the switching device 64.

[0057] In the exemplary embodiment, the manual transmission 63 has no preferred position, so that the manual transmission always retains the last selected gear. The invention encompasses other embodiments with a preferred position of the manual transmission, which are implemented, for example, by means of a second spring device.

[0058] When the adjusting sleeve 32 is rotated, the drive sleeve 30 rotates according to the currently set switching stage. The drive sleeve 30 screws the threaded spindle 20 into the internal thread 22 fixed to the housing, and the upper stop 25 moves up or down depending on the direction of rotation. This adjusts the distance between the upper stop 25 and the lower stop 58, which determines the dosing volume. The currently set dosing volume can be read off the counter 45, which is driven by the drive sleeve 30 via the drive gear 47.

[0059] At the upper edge of the upper housing part 4, next to the adjusting sleeve 32, there is an ejector button 66 on an ejector rod 67. The ejector rod 67 runs parallel to the lifting rod 17 through the upper housing part 4. Its lower end is connected to a lateral fastening projection 68 of an ejector sleeve 69, which is slidably arranged on the projection 6.

[0060] An ejector spring 70, designed as a helical spring, is arranged in the upper housing part 4. One end of the ejector spring is supported in the housing 2 and the other end engages the ejector rod 67. The ejector spring 70 presses the ejector rod 67 upward, so that the ejector sleeve 67 rests against the projection 6.

[0061] The lower housing part 3 and the upper housing part 4 are connected to each other by a snap connection 71.

[0062] Before pipetting, the user can set the desired dosing volume. To do so, turn the adjustment ring 33 until the desired dosing volume is displayed on the counter 45. To set the dosing volume, the user can choose between two speed levels. Especially if the last set dosing volume differs significantly from the dosing volume to be set, the user can initially select a fast speed level. If the gearbox is not already set to the fast speed level, the user grasps the adjustment ring 33 and pulls the adjustment sleeve 32 from the fine adjustment position of Fig. 3 slightly further out of the housing 2 into the Fig. 4 shown quick adjustment position.

[0063] In the quick adjustment position, the first toothing 31 of the drive sleeve 30 meshes with the fourth toothing 40 of the transmission shaft 39 and the third toothing 35 of the adjustment sleeve 32 meshes with the sixth toothing 42 of the transmission shaft 39. As a result, the rotational speed of the adjustment sleeve 32 is translated into a higher rotational speed of the drive sleeve 30, so that the user can quickly adjust the dosing volume close to the dosing volume to be set.

[0064] For precise adjustment of the desired dosing volume, the user can select a slow switching stage. To do this, he presses the adjusting sleeve 32 on the adjusting ring 33 deeper into the housing 2 until it reaches the Fig. 3shown fine adjustment position. In this position, the first toothing 31 meshes with the fourth toothing 40, and the second toothing 34 meshes with the fifth toothing 41. This results in rotation of the adjusting sleeve 32 at a specific rotational speed causing the driving sleeve 30 to rotate at a lower speed than in the fast switching stage. With the toothings of the exemplary embodiment, the rotational speed of the adjusting sleeve 32 is equal to the rotational speed of the driving sleeve 30, since the first toothing 31 and the second toothing 34, as well as the fourth toothing 40 and the fifth toothing 41, each have the same number of teeth and diameter.

[0065] Before or after precisely setting the dispensing volume, the user can clamp a pipette tip 8 onto the pipette 1 by pressing the pipette 1 with the seat 7 into the upper opening 72 of the pipette tip 8. To pipette, the user first presses the operating button 18 downwards so that the stop element 26 is moved from the upper stop 25 against the lower stop 58. The lifting rod 17 presses the displacement element 12 downwards and the first spring device 15 is preloaded. The user then immerses the pipette tip 8 with its lower opening 73 into the sample liquid and releases the operating button 18. As a result, the first spring device 15 presses the displacement element 12 and the lifting rod 17 upwards until the stop element 26 rests against the upper stop 25. A quantity of liquid corresponding to the set dosing volume is sucked into the pipette tip 8.

[0066] To dispense the amount of liquid, the user holds the pipette tip 8 with the lower opening 73 over another container and presses the operating button 18 downwards again. After reaching the lower stop 58, the user can press the operating button 18 even further, overcoming the resistance of the overtravel spring 60, to expel a residual amount of liquid from the pipette tip 8.

[0067] A further amount of liquid can then be pipetted in the same manner, or, to change the sample liquid, the pipette tip 8 can be ejected downward by pressing the ejector button 66. The ejector sleeve 69 then strips the pipette tip 8 from the seat 7. After the ejector button 66 is released, the ejector spring 70 returns the ejector rod 67 to the starting position shown.

[0068] Subsequently, further pipetting operations can be carried out with the same set dosing volume or with a newly set dosing volume, whereby the setting can be carried out as described above.

[0069] Based on the Fig. 6 to 12 The coupling device 74 and the adjustment device 75 are explained in more detail below, which are shown in the Fig. 1 to 5 are omitted for simplicity.

[0070] The coupling device 74 comprises the axle 76, on which the two spur gears 48, 49 are mounted for rotation about a rotation axis 77. The axle 76 is mounted in a first bearing 78, which is formed in the first carrier 24 and the second carrier 44, so that it can be translationally displaced in the direction of the rotation axis 77. The spur gear 49 with the larger diameter is rotationally fixedly connected to the spur gear 48 with the smaller diameter and forms a driving first gear 79 of the coupling device 74. The drive pinion 50 meshing with the spur gear 49 forms a driven second gear 80 for driving the counter 45.

[0071] Furthermore, the coupling device 74 comprises a cam gear 81 which has a first gear element 82 in the form of a first curve 83 which is rotatably mounted on the axis 76 and a second gear element 84 in the form of a second curve 85 which is fixed in position in the housing 7 on the underside of the first carrier 24.

[0072] The first gear element 82 is connected at the bottom in a rotationally fixed manner to a rotary lever 86 having a cam-shaped end 87. A first spring device 88 in the form of a helical spring 89, guided on the axis 76, is supported at the bottom on the first support 24 and at the top on the underside of the spur gear 49. The first support 24 forms an abutment 90 for the first spring device 88. The first spring device 88 presses the spur gear 49 into a position in which it meshes with the drive pinion 50 (see Fig. 6 ).

[0073] The spur gear 49 can be disengaged from the drive pinion 50 by moving the axis 76 downwards against the action of the first spring device 88.

[0074] The adjustment device 75 comprises a second bearing 91 in the form of a bearing body 92, which has a U-shaped cross-section in a horizontal section and a circular first through-hole 93 in the base 94. The bearing body 92 is attached to the side of the first support 24. A first wheel 95 of the adjustment device 75 is rotatably and axially displaceably mounted in the bearing body 92. The first wheel 95 has a protruding hollow cylinder 96 on its outer side, which is rotatably and translationally displaceably mounted in the first through-hole 93 of the bearing body 92 and protrudes outward from the outer side of the bearing body 92. A tool engagement portion 97 is formed in the hollow cylinder 96. The tool engagement portion 97 has the shape of a circular second through-hole 98 with a chord-shaped circumferential section.

[0075] The first wheel 95 is a first friction wheel 99 of a friction gear 100 and consists, for example, of a metal or a plastic.

[0076] Furthermore, the adjustment device 75 comprises a second wheel 101, which is non-rotatably connected to the initial roller of the counter 45 below the number rollers 51. The second wheel 101 is a second friction wheel 102 of the friction gear 100. It is formed, for example, by a rubber ring.

[0077] The housing 2 of the pipette 1 has a housing opening 103 which is centrally aligned with the first and second through holes 93, 98.

[0078] An adjustment tool 104 has a shaft 105 with a profile adapted to the tool engagement portion 97 of the first wheel 95. For this purpose, the shaft 105 has a circular profile with a chord-shaped section in a cross-section through the shaft 105. A handle 106 is connected to the outer end of the shaft 105.

[0079] In Fig. 8 The adjustment tool is shown before insertion into the pipette 1. The spur gear 49 meshes with the drive pinion 50, and the axle 76 is displaced upward to its maximum and is held in this position by the first spring device 88. The rotary lever 86 is rotated by the cam gear 81 into a position in which it presses against the inside of the first gear 95, and this gear presses against the inside of the base 94 of the bearing body 92.

[0080] According to Fig. 6 and 9 The adjustment tool 104 is inserted laterally into the housing opening 103 of the pipette 1, so that the shaft 105 engages the tool engagement 97 of the first wheel 95. Due to the coordinated profiles of the shaft 105 and the tool engagement 97, they are firmly connected to each other in rotation (torsionally fixed). When the shaft 105 is inserted, it pivots the rotary lever 86.

[0081] As a result, the first curve 83 of the cam mechanism 81 is displaced over the second curve 85 and the axis 76 is displaced slightly downwards in a translational manner (cf. Fig. 7 ). This disengages the spur gear 49 from the drive pinion 50 (see Fig. 10 ).

[0082] Finally, by further inserting the adjustment tool 104 into the pipette 1, the handle 106 hits the hollow cylinder 96 and displaces the first wheel 95 further inward into the bearing body 92. In this case, the rotary lever 86 can also be pivoted further (see Fig. 11 ). The first wheel 95 comes into contact with the second wheel 101, so that the setting of the counter 43 can be changed by rotating the adjustment tool 104 (cf. Fig. 12 ).

[0083] Since the counter 45 is decoupled from the adjustment sleeve 32 and the upper stop 25, the lifting system of the pipette 1 is not adjusted. However, the decoupling of the counter 45 from the adjustment device can also be used to adjust the lifting system by adjusting the adjustment sleeve 32.

[0084] After pulling out the adjustment tool 104, the spur gear 49 is brought back into engagement with the drive pinion 50 by the first spring device 88 and the rotary lever 86 and the first wheel 95 are moved into the position according to Fig. 8 shifted. Pipette 1 is then readjusted and can be used for pipetting. List of reference symbols

[0085] 1 Pipette 2 Housing 3 Housing base 4 Housing top 5 Base body 6 Attachment 7 Seat 8 Pipette tip 9 Displacement chamber 10 Connecting channel 11 Opening 12 Displacement element 13 Sealing system 14 Plate 15 Spring device 16 Closure cap 17 Lifting rod 18 Operating knob 19 Spindle bore 20 Threaded spindle 21 External thread 22 Internal thread 23 Lifting body 24 First carrier 25 Upper stop 26 Stop element 27 Driver 28 Ribs 29 Grooves 30 Driver sleeve 31 Toothing 32 Adjusting sleeve 33 Adjusting ring 34 Second toothing 35 Third toothing 36 Disc 37 Lower limit 38 Upper limit 39 Transmitter shaft 40 Fourth toothing 41fifth toothing 42sixth toothing 43toothing 44second carrier 45counter 46counter roller axle 47drive gear 48,49Spur gear 50Drive pinion 51Number roller 52Window 53Cover 54Holder 55External thread 56Internal thread 57Third carrier 58Lower stop 59Upper wheel 60Overtravel spring 61Base 62Spur gear 63Switching gear 64Switching device 65Switching element 66Ejector button 67Ejector rod 68Fastening lug 69Ejector sleeve 70Ejector spring 71Snap connection 72Upper opening 73Lower opening 74Coupling device 75Adjustment device 76Axle 77Rotary axis 78First bearing 79First gear 80Second gear 81Cam gear 82First gear element 83First curve 84Second gear element 85Second curve 86Rotary lever 87Cam-shaped End 88First spring device 89Coil spring 90Abutment 91Second bearing 92Bearing body 93First through hole 94Base 95First wheel 96Hollow cylinder 97Tool attachment 98Second through hole 99First friction wheel 100Friction wheel gear 101Second wheel 102Second friction wheel 103Housing opening 104Adjustment tool 105Shaft 106Handle,

Claims

1. A pipette having an adjustable dosing volume, comprising • a rod-shaped housing (2), • at least one seat (7) for releasably holding a pipette tip (8) at the lower end of the housing (2), • a displacement apparatus comprising a displacement chamber (9) having a displacement element (12) that can be moved therein, • a connection channel (10) that connects the displacement chamber (9) to an opening (11) in the seat (7), • a stroke rod (17) that is coupled at the lower end to the displacement element (12) and that can be moved in the housing (2) in the longitudinal direction for moving the displacement element (12) in the displacement chamber (9), • an operating button (18) that is connected to the upper end of the stroke rod (17) and that projects from the housing, • a stop element (26) on the outer periphery of the stroke rod (17), • an upper stop (25) for the stop element (26) and a lower stop (58) for the stop element (26) in order to limit the stroke of the stroke rod (17), • a setting apparatus (32) for setting the position of the upper stop (25) in the housing (2), • a display apparatus (45) for displaying a set dosing volume, • a form-fitting coupling apparatus (74) between the setting apparatus (32) and the display apparatus (45) which is designed, in an engaged state, to couple the setting apparatus (32) to the display apparatus (45) and, in a disengaged state, to decouple the setting apparatus (32) from the display apparatus (45), • an adjustment apparatus (75) that is designed to change the setting of the display apparatus (45) when the coupling apparatus (74) is decoupled, • characterized in that • the coupling apparatus (74) is designed such that it can be engaged and disengaged by inserting an adjustment tool (104) into the housing (2) from the outside of the housing (2), • the adjustment apparatus (75) is designed such that the setting of the display apparatus can be changed from the outside of the housing (2) by means of an adjustment tool (104) when the coupling apparatus (74) is decoupled, and • the same adjustment tool (104) can be inserted into the housing (2) through the same housing opening (103) of the housing (2) in order to decouple the setting apparatus (32) from the display apparatus (45) and to change the setting of the display apparatus (45).

2. The pipette according to claim 1, wherein the coupling apparatus (74) and the adjustment apparatus (75) are designed such that, by introducing an adjustment tool (104) into the housing (2), firstly the coupling apparatus (74) can be decoupled and the setting of the display apparatus (45) can be changed by introducing the adjustment tool (104) deeper and then rotating same.

3. The pipette according to any one of claims 1 to 2, wherein the coupling apparatus (74) comprises a driving first gear wheel (79) that is coupled to the setting apparatus (32) and that is mounted so as to be rotatable about an axis of rotation, a shaft (76) that is mounted in a first bearing (78) in the housing (2) so as to be movable in translation in the direction of the axis of rotation and that supports the first gear wheel, a driven second gear wheel (80) of the display apparatus (45) that meshes with the first gear wheel (79), a cam mechanism (81) having a first mechanism element (82) that is supported by the shaft (76) and having a second mechanism element (84) that is supported in a stationary manner in the housing (2), and a rotary lever (86) that is connected to the first mechanism element (84) for conjoint rotation therewith, wherein the first gear wheel (79) is held on the shaft (76) so as to be prevented from moving upwards on the shaft (76) and the first mechanism element (84) is held on the shaft so as to be prevented from moving downwards on the shaft (76) and, by pivoting the rotary lever (86), the shaft (76) can be moved in translation via the cam mechanism (81) and the first gear wheel (79) can be brought out of engagement with the second gear wheel (80) in order to decouple the setting apparatus (32) from the display apparatus (45).

4. The pipette according to claim 3, wherein the first mechanism element (82) is a first cam (83) and / or wherein the second mechanism element (84) is a second cam (85).

5. The pipette according to claim 2 or 3, wherein the rotary lever (86) can be pivoted by inserting the adjustment tool (104) through a housing opening (103) of the housing (2).

6. The pipette according to any one of claims 3 to 5, wherein a first spring apparatus (88) is arranged between the shaft (76) and a counter-bearing (90) that is arranged in a stationary manner in the housing (2), the first spring apparatus (88) presses the shaft (76) with the first gear wheel (79) into a position meshing with the second gear wheel (80), and the first gear wheel (79) can be brought out of engagement with the second gear wheel (80) counter to the effect of the first spring apparatus (88).

7. The pipette according to any one of claims 2 to 6, wherein the adjustment apparatus (75) comprises a driving first wheel (95) that is mounted in a second bearing (91) in the housing (2) so as to be rotatable about an axis of rotation and movable in translation in the direction of the axis of rotation and that is accessible from the outside of the housing (2) in order to move the first wheel (95) until it abuts a driven second wheel (101) that is coupled to the display apparatus (45), to rotate the second wheel (101) by rotating the first wheel (95), and to change the setting of the display apparatus (45).

8. The pipette according to claim 7, wherein the first wheel (95) can be moved up to the second wheel (101) by inserting the adjustment tool (104) into the housing (2) and the first wheel (95) and the second wheel (101) driven thereby can be rotated by rotating the adjustment tool (104).

9. The pipette according to claim 7 or 8, wherein the first wheel (99) and the second wheel (101) are a first friction wheel (101) and a second friction wheel (102) of a friction wheel mechanism (100).

10. The pipette according to any one of claims 7 to 9, wherein the first spring apparatus (88), via the shaft 76) and the unloaded rotary lever (86), presses the first wheel (95) away from the second wheel (101) until it abuts the second bearing (91).

11. The pipette according to any one of claims 1 to 10, wherein the coupling apparatus (74) and the adjustment apparatus (75) is designed for actuation by means of an adjustment tool (104) which comprises a shank (105) having a profile that is adapted to the tool engagement portion (97) of the first wheel (95) and a handle (106) that is connected to the shank (105) for conjoint rotation therewith, in order to pivot the rotary lever (86) by introducing the shank (105) into a housing opening (103) of the housing (2), to enter into a connection for conjoint rotation with the driving first wheel (95), to bring the first wheel (95) into frictional connection with the second wheel (101) by introducing the shank (105) further, and to rotate the second wheel (101) by means of the first wheel (95) by rotating the adjustment tool (104).

12. A set comprising a pipette according to any one of claims 1 to 11 and an adjustment tool (104), wherein the adjustment tool (104) comprises a shank (105) having a profile that is adapted to the tool engagement portion (97) of the first wheel (95) and a handle (106) that is connected to the shank for conjoint rotation therewith, in order to pivot the rotary lever (86) by introducing the shank (105) into a housing opening (104) of the housing (2), to enter into a connection for conjoint rotation with the driving first wheel (95), to bring the first wheel (95) into frictional connection with the second wheel (101) by introducing the shank (105) further, and to rotate the second wheel (101) by means of the first wheel (95) by rotating the adjustment tool (104).