EP0364621B1 - Pipetting device - Google Patents

Abstract

A pipeting device has at the top an actuating element (2) which can be pressed in against spring action and is connected to a piston moveable in a cylinder in order to move a volume of air. The cylinder communicates with an opening in a connection piece, in particular a connection cone, for attachable pipette tips which are open at the top and at the bottom. By twisting the actuating element (2) the pipetting volume can be adjusted. In addition, the button-like actuating element (2) is also provided for releasing a locking element catch, which can be lifted out axially, between a spindle (6) and an abutment, integral with the housing, as threaded insert and the said piston is, in a manner known per se, progressively adjustable by twisting the button-like actuating element (2) in a spindle drive (6) of a piston rod (7) for the piston. At least one of the locking elements (31, 32) is arranged distributed around the circumference of the centre axis of the pipetting device, it being preferred for the locking element catch to be designed with two toothed rings (31, 32) which are arranged on the parts of the pipetting device to be moved relatively to one another. <IMAGE>

Description

The invention relates to a pipetting device with a housing, at the upper end of which protrudes an actuating element which can be pressed in against spring action and which is connected to a piston which can be moved in a cylinder in order to move an air volume which cylinder has an opening of a connecting attachment, in particular a connecting cone. for pluggable pipette tips which are open at the top and at the bottom, settings of the pipetting volume being provided by rotating the actuating element.

Such pipetting devices are known. The invention is based in particular on a pipetting device according to DE-P 25 49 477, in which special holding devices, also as a magnet arrangement, are provided and in the lower region a piston rod can be moved within a cylinder in order to, with respect to the lower, open housing end, in which the cylinder ends up moving an air volume in order to draw in or dispense a liquid sample to the piston without contact.

In this known embodiment, cam-like stops which are offset around the circumference and which can be arranged at different heights are arranged for volume adjustment. These stops can be set using a mechanical locking device on the actuating element, in particular an actuating button for adjustment in abutment with an abutment, so that a selected pipetting volume can thereby be predetermined.

The arrangement of springs is also known from the known embodiment in order to produce the connection of interacting parts, unless a magnet arrangement is present.

This known design allows only a gradual adjustment of the pipetting volume.

It is also known, for example from DE-AS 28 08 649, to carry out a continuous adjustment, the piston rod being provided in a tube arrangement which has an external tube thread, and furthermore a sleeve screwed onto the tube by relative Rotation between the parts can be moved back and forth, so that ultimately the piston is also continuously adjustable. However, this requires that a so-called tightening nut must be loosened and tightened again with each setting. This design is therefore complex and also requires considerable care during operation.

From DE-OS 29 21 442 an adjustable pipette is known in which a screwable sleeve is also arranged. The entrainment takes place via a plate-like spread at the lower end of a piston rod, the connection to the piston being established by spring pressure.

This embodiment works unsafe per se, especially since it allows longitudinal grooves on the outer surface of the sleeve to interact with a closure tip which is pressed by a leaf spring. So there is a catch-like snap connection, which on the one hand has no fine adjustment, on the other hand also causes noise.

From DE-P 112 887 a locking device is known on a pipette with adjustable volume, which has spherical projections which cooperate with corresponding recesses, which are arranged in another part, so that volume adjustment is possible. This is also a coarse screen, the adjustment of which causes noise and does not allow fine adjustment.

It is also known from DE-OS 31 37 423 for a µ1 pipette to arrange a brake in order to obtain a set volume. Such a brake can be overcome. On the one hand, it hinders easy adjustment and, on the other hand, would reduce the setting security if the pressure was too low.

The known devices with fine adjustment are subject to the disadvantage that the respective volume fixation is uncertain. There is also the risk of a so-called "overturning", in which parts are then damaged.

The invention has for its object to provide a pipetting device of the type mentioned, which allows fine adjustment, but a safe setting and easy, but also reliable operation are guaranteed.

This object is achieved in that a locking element engagement between a spindle and a housing-mounted abutment can be axially lifted by means of the preferably button-like actuating element and by rotating the actuating element when the locking element engagement is lifted, the spindle with a piston rod for the piston in a housing-fixed thread insert with a corresponding change the pipetting volume is infinitely adjustable.

What is essential is the release of the locking element engagement for stepless adjustment, the release being effected by means of an axial lifting movement by means of the button-like actuating element, which can also be rotated for peripheral adjustment after the lifting. In this case, an actuating element is used to both release the locking and to make the adjustment.

The detachable locking engagement in connection with a stepless adjustability creates the prerequisite for a particularly inexpensive pipetting device that is fixed in the setting, but can be freely selected in practice. If a locking engagement is mentioned, these are detents of the finest kind.

At least one of the locking elements is advantageously arranged distributed around the circumference of the central axes of the pipetting device.

With this circumferential distribution, any circumferential setting can be realized. It is preferred that both locking elements are arranged distributed around the circumference, because then - which is advantageous for particularly fine settings - a radially symmetrical intervention is reserved, which, however, can be canceled by axial movement according to the above explanations or can be engaged again by opposite axial movement.

The locking element engagement is particularly advantageously carried out with two toothed rings which are arranged on the parts of the pipetting device which are to be moved relative to one another. The use of sprockets has the advantage of being relatively easy to manufacture with the finest division. Such a locking element engagement works in the preferred embodiment with a tooth pitch that allows the smallest circumferential rotation steps, but in another expedient embodiment is also directly matched to a volume setting. An adjustment by a tooth pitch would bring about the smallest selectable volume adjustment.

The fineness of such an adjustment results from a configuration of the engagement elements in the form of lamellae.

Another expedient version provides a tooth depth of approximately 1.5 mm for reliable tooth engagement. This also enables a largely fine tooth division.

This creates a combination between a stepless spindle drive and gear meshing.

It is preferred that a toothing engagement in the axial direction is provided with a ring gear which has upwardly directed teeth into which a ring gear engages from above on a carrier for the actuating element. This is an advantageous embodiment.

In another advantageous embodiment, a toothing engagement is provided in a toothed ring designed in the radial direction, to which a corresponding counter toothed ring on the spindle is assigned so that it can be lifted out in the axial direction.

This results in two basic embodiments for an axial and a radial arrangement of the tooth engagement, but there is always a lifting movement in the axial direction of the pipetting device.

The locking element engagement preferably takes place on a locking disc which is prevented from rotating by the housing-side abutment about the central axis of the pipetting device.

Another particularly advantageous feature is that a friction or slip clutch is arranged between the knob-like actuating element and the spindle, which allows an actuation element rotation with existing engagement of the locking element. This protects the fine toothing or protects it from destruction, even if the button-shaped actuating element is rotated at will.

If it is written above that axially removable locking elements, then a particularly advantageous embodiment is that the axially removable engaging elements also have locking profiles as teeth, which are designed to be able to be overcome in order to maintain the engagement.

This applies to both axial and radial engagement. It is preferred that the latching profiles are designed with mutual thickening at their ends in the sense of the engagement and lifting direction and that these thickenings are arranged on elastic tooth-like webs.

When mutually thickening is arranged on both latching elements with the possibility of elastic evasion, there are safe interventions, in particular what is preferred if the thickenings are arranged with staggering or with each other in front and back. This makes it possible for the engagement to be produced when profiling elements which can be pushed into engagement are moved symmetrically toward one another and in the process a deflection movement is first triggered on a thickening in a circumferential row and this evasive movement is then canceled and locked again when other thickenings on tooth-like webs follow .

The thickenings are expediently spherical beads.

According to another advantageous embodiment, the thickenings have a conical shape with opposite slopes with respect to the parts that come into engagement with one another. Mutual interventions can also be achieved in this way, provided that the thickenings are arranged on elastic webs.

It is useful that a piston rod is provided between the piston and the upper end of the button-shaped actuating element and has a stop on the spindle, which limits the maximum position of the piston rod with respect to the spindle and in the button-like actuating element. This stop, too, is protected against damage from the friction or slip clutch when it is engaged.

Here, a further advantageous embodiment is that the friction or slip clutch between the button-like actuating element and the toothed carrier of the button-like actuating element is arranged in the circumferential direction and has an elastic element with indentations, in which engage corresponding elastic engagement elements of the counter-coupling element, one Coupling element designed as a button carrier is guided for tooth engagement and the other coupling element is arranged on the rotatable button-like actuating element.

This is a particularly simple embodiment which, however, certainly allows the button-like actuating element to be turned relatively easily and thus represents a special configuration of the friction clutch.

In a particularly favorable embodiment, a carrier which is guided in a rotationally fixed manner in the housing has axially directed spring elements which engage like tongues with engagement lugs in ring grooves of the piston rod, the engagement between different ring grooves being variable as a function of a pull-out position of the button-like actuating element. As a result, settings that can be felt for the respective function of the button-like actuating element can also be achieved for the operator.

The latter is designed in two parts with particular advantage, but both parts are non-rotatably connected to one another and an elastic insert of the upper part is provided on the towering piston rod with spring elements which can be spread outwards and which engage under abutment parts in the carrier of the button-like actuating element.

It is further preferred that the friction or slip clutch consists of groove-like incisions on an upwardly projecting cylindrical extension of the intermediate element and inwardly directed webs on downwardly directed edge parts of the cover shell.

In an advantageous embodiment, teeth of the load elements are lamellar and are provided for a lateral evasive movement.

It is preferred that the locking profiles are formed on one side. In a favorable embodiment, the profiles protrude on one gear rim and are designed as negative profiles on the other gear rim.

Another particularly expedient embodiment provides that the two ring gears are arranged on circumferential circles with different radii, with opposing beads overlapping on the respective toothings and providing elastic resilience of the teeth, in particular also in the radial direction.

The invention is described below using an exemplary embodiment which is illustrated in the drawing.

Fig. 1

als Figuren 1 a und 1 b, welche untereinander anzuordnen sind:
eine im Schnitt dargestellte Seitenansicht des oberen Teils der Pipettiervorrichtung;

Fig. 2

einen Einzelteil aus Fig. 1 im Schnitt längs der Linie II-II in Fig. 3;

Fig. 3

eine Ansicht der Fig. 2 von unten;

Fig. 4

eine Seitenansicht der Fig. 2;

Fig. 5

eine Seitenansicht eines Einzelteiles aus Fig. 1 und im Schnitt;

Fig. 6

eine Ansicht auf Fig. 5 von oben;

Fig. 7

eine Seitenansicht eines Mitnehmers in dem Gehäuse der Pipette im Schnitt;

Fig. 8

die Seitenansicht eines Zwischenelementes im Schnitt;

Fig. 9

eine Draufsicht auf Fig. 8;

Fig. 10

eine Abwandlung der oben beschriebenen Verzahnung im Schnitt dahingehend, daß am gehäusefesten Teil eine radial nach außen gerichtete Verzahnung angeordnet ist, in welche eine am Knopfträger in seinem zylindrischen Mantel radial nach innen gerichtete Verzahnung eingreift;

Fig. 11

eine Draufsicht auf eine Verzahnungsanordnung mit Rastelementen;

Fig. 12

eine Seitenansicht eines Ausschnittes aus dieser Verzahnung;

Fig. 13

eine Teilansicht einer anderen Ausführung der Verzahnung mit kegelförmigen Verdickungen.

The drawing shows:

Fig. 1

as Figures 1 a and 1 b, which are to be arranged one below the other:
a sectional side view of the upper part of the pipetting device;

Fig. 2

an individual part of Figure 1 in section along the line II-II in Fig. 3.

Fig. 3

a view of Figure 2 from below.

Fig. 4

a side view of Fig. 2;

Fig. 5

a side view of an item of Figure 1 and in section.

Fig. 6

a view of Figure 5 from above.

Fig. 7

a side view of a driver in the housing of the pipette in section;

Fig. 8

the side view of an intermediate element in section;

Fig. 9

a plan view of Fig. 8;

Fig. 10

a modification of the toothing described above in section in that a radially outwardly directed toothing is arranged on the housing-fixed part, in which engages a toothing directed radially inward on the button carrier in its cylindrical jacket;

Fig. 11

a plan view of a gear arrangement with locking elements;

Fig. 12

a side view of a section of this toothing;

Fig. 13

a partial view of another embodiment of the toothing with conical thickenings.

In the following, Figures 1 a and 1 b are collectively referred to as Fig. 1.

1 shows the pipetting device only partially, namely with the upper part of the housing 1, from which an actuating element 2 protrudes in the middle upwards as a pushing and rotating lever or correspondingly actuatable button.

From the above-mentioned DE-P 25 49 477 it is known that a special volume is to be set there by means of a piston rod and its rotation by means of an actuating button, stops offset around the circumference only permitting a gradual adjustment of the volume.

The now provided stepless adjustment provides that in the housing 1 a threaded insert 3 by screwing firmly in the circumferential and in the axial direction cannot be relocated, namely by a screw thread 3 'and in its internal thread 4 an external thread 5 of a spindle 6 can be rotated . The piston rod 7 passes through the spindle in the axial direction without a rotary connection. This piston rod 7 abuts with its upper end 8 on the cover 9 of the button-like actuating element 2, which is initially referred to as such up to a lower edge 10.

This lower edge is supported on a button holder 11, which can also be seen more clearly from FIG. 2. The actuating element 2 is connected in one piece in the axial direction to the button carrier 11 by expandable spring elements 12, 13 on the cover shell, the outwardly directed contact pieces 14, 15 of the spring elements at the same time ensure the cohesion between the parts 9 and 11 because the abutment parts 16, 17 are arranged on the button holder 11.

The button carrier 11 has a guide 18 inside made of spring arms 19, 20, as can also be seen in FIG. 2, and which are delimited from one another by longitudinal slots 48. The piston rod 7 passes through this guide. It has two circumferential recesses 21, 22 one above the other at a distance. Inward engagement shoes 23, 24 engage in these circumferential recesses at the lower ends of the spring arms 19, 20. It can be seen that the piston rod can thus in each case be rotated but can be changed in the axial direction in two different positions relative to the actuating element 2.

A stop disk 25 is also arranged on the piston rod 7 and forms a stop between the piston rod 7 and the lower edge of the spring arms 19, 20 or the engagement shoes 23, 24 arranged on them. This abutment prevents the piston rod 7 from migrating too far upwards with respect to the actuating element 2, or it forms a stop for pressing the piston rod 7 downward when the actuating element 2 is pressed in again.

A spring abutment 27 for a compression spring 28 is arranged on the piston rod just below the upper head, which is supported on the other hand via a washer 29 on the intermediate web 30 of the button carrier 11. However, this is only a uniform and elastic engagement standing version of the actuating element 2 created by pressing the spring elements 12, 13 after their insertion against the stops of the abutment parts 16, 17. The cover shell 9 can be pulled out together with the actuating element 2, taking the button carrier 11 with it, so that the engagement shoes 24 are removed from the peripheral recess 21 and can be latched into the peripheral recess 22. This is achieved in that a stop 42 bears against the piston rod 7 at the lower end of the spindle 6.

When this is carried out and the actuating element 2 is rotated, the button carrier 11 is carried along by a friction clutch. The engagement of such a friction or slip clutch 73 has the sense that even if a toothed connection is engaged, further rotation is possible without destroying a very fine toothing. This friction or slip clutch, generally designated 73, will be described later. This is an advantageous embodiment. A rigid entrainment is not excluded.

With this pull-out movement, lower teeth 31 (see also FIGS. 2 and 4) are simultaneously lifted out of counter teeth 32 of a locking disk 33 (FIGS. 5 and 6) in housing 1. At the same time, the engagement in radially inward grooves 36, 37 of a driver 38 is maintained by means of the radially inward webs 34, 35. This driver 38 is shown in detail in FIG. 7. The driver 38 has an internal thread 49 which is screwed onto an external thread 50 at the upper end of the spindle 6. As a result, the inwardly directed grooves 36, 37 on the driver 38 are connected in a rotationally fixed manner to the spindle 6, so that through the engagement of the webs 34, 35 the spindle is taken along when the actuating element 2 is rotated, as long as the friction clutch 73 remains engaged.

It is also noted that the inward grooves in the axial direction are longer than the extent of the teeth 31 and counter teeth 32 in the axial direction. This means that the slewing ring is retained even when these teeth are disengaged.

The engagement of the webs 34, 35, however, can only be canceled by pulling the actuating element 2 upwards because the actuating element 2 is held in the peripheral recess 22 with the button carrier 11 by engagement of the engagement shoes 23, 24, so that when the trigger is finally removed for the purpose of disassembly this intervention must also be overcome. In this regard, it is noted that in the area of the lugs 46, 47 which are still to be mentioned, there is also a cover on the protruding part 54 upwards and this cover, which can cover a counter, would first have to be removed during disassembly. However, this is not part of the present invention.

The locking disk 33 is displaceable relative to the driver 38 and has projections 40 which engage in grooves 39 in the housing 1, so that the locking disk 33 can be pressed downward along the housing 1. Between the threaded insert 3 and the locking disk 33 there is a compression spring 41 which tends to push the locking disk upwards. As a result, the engagement between the toothed parts 31, 32 is maintained. So that the locking disc 33 is rotatably but resiliently held in the axial direction, but only to the extent that the engagement of the projections 40 with the downwardly angled legs remain in the grooves 39, even if the button-like actuating element is pulled out until the stop disk 25 abuts the lower edges of the engagement shoes 23, 24.

3 shows the toothing 31, the lugs 46, 47 being shown at the same time. Furthermore, the inwardly directed webs 34, 35 are shown, it being apparent from FIG. 3 that corresponding parts which are offset by 90 ° are present, the webs 70, 71 engaging in inwardly directed grooves of the driver 38.

This driver, of which a side view is shown in FIG. 7, has a circumferential configuration which results from FIG. 3, wherein it can be seen that a configuration is provided with regard to the circumference in the sense of the stability of the arrangement.

If the actuating element 2 is pulled out upwards, an engagement on the toothings 31, 32 is released and the actuating element 2 can be rotated while driving the spindle 6 due to the engagement between the parts 34, 35 and 36, 37. As a result, the spindle 6 is taken along and it changes its axial position within the threaded insert 3, so that the piston rod 7, which abuts on the lower edge 43 of the so-called spindle by means of a stop 42, is taken along, on account of the action of the spring 41 on the one hand and the spring 28 on the other hand. The vertical movement of the spindle and the associated parts is limited by an annular disc 44, which acts as a stop bears against the lower surface 45 of the threaded insert 3. As a result, the spindle 6 cannot move upward unrestrictedly to the actuating element 2, but can at most stand down from the lower surface of the threaded insert 3.

If this is taken as the starting position, as shown in the drawing in FIG. 1, the actuating element 2 can be pulled upwards, the engagement shoes 23, 24 engaging in the upper peripheral recess. At the same time, the outwardly directed lugs 46, 47 move upwards in grooves in an insert 51. The insert 51 is supported and held on a step 53 of the housing 1 with an extension projecting outwards and forming a shoulder 52. The holder is carried out by the part 54, not shown in FIG. 1, on the upper side of the housing.

The piston rod 7 ends in a rotationally fixed manner on a component 55. The continuing piston rod or the piston 56 is arranged there, which according to the mentioned DE-P 25 49 477 then ultimately also extends with extensions into the lower connecting cone or into one that continues Channel engages in order to bring about the suction effect or expression via an air volume.

The internal thread 57 of the housing now gives the possibility of connecting further housing parts, and in the area 58 there can be special holding devices which, according to DE-P 25 49 477, are designed as overcomeable holding devices, in particular in the embodiment as a separable magnet arrangement. As a result, a certain setting is infinitely defined in a simple manner with the advantageous magnet arrangements.

In this sense, the piston rod 7 can be moved downward from the lower edge 43 of the spindle, but not upwards. If the pipetting volume is to be reduced from the starting position shown, which represents the largest pipetting volume, the actuating element 2 can be pulled upwards so that the engagement shoes 23, 24 engage in the circumferential recess 22. Thus, the toothing at 31, 32 is disengaged and the spindle can be freely rotated by rotating the actuating element 2 in the direction of the downward movement, the piston rod 7 being carried downward. After sufficient rotation, the actuating element is pressed in again, so that the engagement shoes 23, 24 engage in the peripheral recess 21.

If, during the rotation in the spindle, the height setting, which is formed by the stop by means of the annular disk 44, is exceeded, a slip clutch 73, which has already been mentioned above, comes into operation. This is an intermediate element 59 between the button holder 11, which is also described in FIGS. 2 and 4, and the cover shell 9. This intermediate element 59 is shown in detail in side view and in section in FIG. 8 and in plan view in FIG. 9 shown.

The side view reveals the outer cylinder 60, which is also present according to FIG. 1 and can be made transparent. It has the inward step 61 on top, which is on the upward step Flange 62 of the button holder 11 supports. The cover shell 9 is held on the upper, outwardly directed step 63 by the engagement of the spring elements 12, 13.

The intermediate element 59 has on the inside of the upper step 63 an upwardly projecting cylindrical extension 64 (FIG. 9), which has groove-like incisions 65, 66 going around the circumference. This protruding projection is elastic.

In these groove-like incisions 65, 66 engage inwardly directed webs 67, 68 on the downward edge parts of the cover shell 9. This provides a flexible snap. This resilient latching holds the intermediate element 59 in a negotiable rotary connection with the cover shell 9. On the other hand, the intermediate element is held by friction at 69 on the button carrier 11, so that in this context the above-mentioned slip clutch is present, which is designated as a whole by 73. It consists of the latching device described with the incisions 65, 66 and the frictional engagement 69. The entrainment that can be overcome is provided by the cover shell 9 and the frictional engagement with the button carrier 11 is also present.

1 shows in the top right and left side different configurations between the inner button carrier and the outer intermediate element 59, so that a groove-like engagement is also conceivable in this connection.

It is also provided that a stop disk 25 on the piston rod is kept free from overloading by the friction or slip clutch. The slip clutch advantageously has an elastic element 64 with indentations into which corresponding elastic engagement elements 67, 68 of the mating clutch element engage, one clutch element 11 leading to tooth engagement and the other clutch element being arranged on the rotatable knob-like actuating element 2.

In this case, a support 11, which is guided in a rotationally fixed manner in the housing, also expediently has axially directed spring elements 19, 20 which engage like tongues with engagement shoes 24, 25 in annular grooves 21, 22 of the piston rod 7, the engagement between different annular grooves 21, 22 depending on an extended position of the button-like actuator 2 is changeable.

In the two-part design of the button-like actuating element, both parts are connected to one another in a rotationally fixed manner, but there is an elastic insert of the upper part on the projecting piston rod 7 with spring elements 12, 13 which can be elastically expanded outwards, which abutment parts 16, 17 in the carrier 11 of the button-like Reach in under the actuator.

The axially movable, guided in the housing locking disc is under spring pressure upwards, namely to rest against a counter bearing at the lower edge of the insert 51 in the housing.

FIG. 10 shows another embodiment of the lower part of the individual part drawn in FIG. 4. It can be seen that this lower part extends to the lower opening 74. Inside the wall 75, inwardly directed teeth 76 are arranged at the opening edge, which can be placed on the ring gear 32, which in this case has an exactly corresponding additional profile in its radial arrangement, so that a particularly fine tooth division is possible.

11 and 12, the mutually engaging tooth parts, which are referred to as toothing and counter toothing above with 31 and 32, are designed in a special way. The toothing 31 is located on the lower edge of the button carrier 11, while the counter toothing 32 is arranged on the insert or the locking disk 33.

FIGS. 12 and 13 each show a section of the locking disk 33 with an upwardly directed, specially designed counter-toothing and also the downward toothing on the button carrier 11, of which only a section is drawn.

It can be seen, for example, from FIG. 12 that the teeth 77, 78, 79 ... corresponding to the counter toothing have a spherical thickening 80, 81; 82, 83 have a corresponding bulge-like thickening 88 to 91, for example, only arranged on one side on the teeth 84 to 87 corresponding to the toothing 31.

As a result of this one-sided arrangement, in the case of an elastic design, for example with teeth 84 to 87, which can be lamella-shaped, there is the possibility of a lateral evasive movement if the profiles 80 to 83 on the one hand and 88 to 91 on the other hand pass one another. This creates a snap connection.

FIG. 11 shows this toothing arrangement in a top view, specifically in section along the line XI-XI in FIG. 12. The teeth 84 to 87 coming from above with the one-sided thickening 88 to 91 can be seen, as is the spherical thickening 80 to 83, which is arranged on the lower teeth 77 to 79.

FIG. 13 shows a representation corresponding to FIG. 12 in a detail. The teeth 92, 93, 94 ... corresponding to the toothing 31 are conical and are arranged in such a way that they can elastically deflect at their roots 95 to 97. Correspondingly, the teeth 98 to 100 of the counter-toothing are designed on the locking disk 33, a tooth spacing or tooth pitch being provided in such a size that a lateral evasive movement is possible during the transition with a snap action when inserting or loosening the toothing.

In the sense of a small division, it is also included, as is shown above at 88 to 91, that the profiling projecting towards the tooth head is only arranged on one side in such a way that there are always two such profiles opposite, while the other side of the tooth can be profiled in the usual way.

It goes without saying that, according to the embodiment according to FIG. 13, the head edges are rounded, so that an evasive movement is brought about when the parts are moved towards one another in the axial direction or are separated from one another.

Corresponding profiles are also possible with a toothing arrangement according to FIG. 10.

These examples according to FIGS. 11 to 13 show designs in which the teeth are on the same circumferential circles. In the sense of a tooth division that is as fine as possible, it is included that the two ring gears are located on circumferential circles with different radii such that they still touch. It is then included here that opposing beads overlap on the respective toothings and accordingly engage with elastic resilience of the teeth, in particular also in the radial direction, with the generation of a cogging torque.

If beads and protruding profiles are shown in the examples, it goes without saying that the latching means can also be designed in such a way that a protruding profile is formed on one sprocket and corresponding negative profiles are formed on the other sprocket, so that the effort for engagement is reduced.

For a radial engagement, as shown with reference to FIG. 10, it is then also possible to design the teeth as pins for which the counter-toothing has a ring gear in the form of snap-in receptacles.

In the case of axial tooth arrangements, it is reserved to reduce the parts that come into engagement with one another, which are designed as toothing and counter-toothing, to a push-button-like design, the counter-toothing being designed in the form of receiving holes with a constricted mouth, which has an elastic edge determined by spring parts , while the engagement toothing has protruding push button parts with a thickened head.

In this context, however, it is included to widen the pipetting device at least in the area of the tooth engagement, so that the circumferential division allows a sufficient fine adjustment with the increased space requirement of such an engagement arrangement.

Claims (22)

1. A pipetting device comprising a housing, an actuating element adapted to be depressed against a spring force projecting from an upper end of the housing, which actuating element is connected to a piston movably arranged in a cylinder to displace an air volume, a connector means, in particular a conical connector for attachable open-ended pipetting tips, said connector having an opening communicating with said cylinder, wherein the pipetting volume is ajustable by rotating the actuating element, characterized in that a detent element engagement between a spindle (6) and an abutment of the housing is axially releasable by the actuating element (2) and that by rotating the actuating element (2) the spindle (6) with the piston rod 7 of the piston (56) is infinitely adjustable by in a threaded insert (3) of the housing to correspondingly select the pipetting volume when the detent element engagement is released.
2. The pipetting device of claim 1, characterized in that at least one of said detent elements (31, 32) is spaced about the periphery of the center axis of the pipetting device.
3. The pipetting device of one of claims 1 and 2, characterized in that the detent element engagement comprises a pair of gear rings (31, 32; 77-79; 84-87; 98-100; 92-94) which are provided at parts of the pipetting device which are movable with respect to each other.
4. The pipetting device of claim 3, chacterized in that a meshing engagement in an axial direction is provided by a gear ring (32) having upwardly extending teeth (77-79; 98-100) which are engaged from upwardly by a gear ring (31) provided on a carrier (11) for the actuating element (2).
5. The pipetting device of claim 2 or 3, chacterized in that a meshing engagement is provided by a radially arranged gear ring (76) cooperating with a gear ring (32) on the spindle (6) to be released in an axial direction.
6. The pipetting device of one of claims 2 to 5, chacterized in that the detent element engagement is provided at a detent disk (33), wherein a rotational movement of the disk is prevented by an abutment (39) of the housing.
7. The pipetting device of one of claims 1 to 6, characterized in that a friction or slipping clutch (73) is provided between the actuating element (2) and the spindle (6) which clutch allows a rotation of the actuating element (2) when the locking engagement is established.
8. The pipetting device of one of claims 1 to 7, characterized in that the axially releasable engaging elements comprise teeth (31, 32; 84-87; 77-79; 92-94; 98-100) defining detent profiles (80-83; 88-91) which can be overcome in the sense of maintaining the engagement.
9. The pipetting device of claim 8, characterized in that the detent profiles (80-83; 88-91) have ends which are alternatively enlarged in the sense of the engaging and disengaging direction and that the enlargements are provided at flexible, teeth-shaped blades.
10. The pipetting device of claim 9, characterized in that the enlargements (80-83; 88-91) are defined by ball-shaped beads.
11. The pipetting device of claim 9, characterized in that the enlargements are defined by a conical profile having opposite slopes with respect to the parts engaging each other (Fig. 13).
12. The pipetting device of one of claims 1 to 11, characterized in that a piston rod (7) is provided between the piston (56) and the upper end of the actuating element (2), said rod having a stop (42) at the spindle (6) to limit the upper position of the piston rod (7) with respect to the spindle (6) as well as in the knob-shaped actuating element (2).
13. The pipetting device of one of claims 7 to 12, characterized in that the friction or slipping clutch (73) is peripherally located between the knob-like actuating element (2) and the meshing carrier (11) of the knob-like element (2) and that an elastical element (94) comprises indentations engaging corresponding elastical engaging elements (67, 68) of the counter clutch element wherein a clutch element defined to be a knob carrier (11) extends towards the meshing engagement and that the other clutch element is located at the rotatable knob-like actuating element (2).
14. The pipetting device of one of claims 1 to 13, characterized in that a carrier (11) non-rotatably guided in the housing comprises axially extending spring elements (19, 20) having engaging shoes (24, 25) for tongue-like engaging annular grooves (21, 22) of the piston rod (7) wherein the engagement between the various annular grooves (21, 22) is selectable in response to a pulling out position of the knob-like element (2).
15. The pipetting device of one of claims 1 to 14, characterized in that the knob-like actuating element (2) consists of two parts, both parts being non-rotatably connected to each other and that an elastic insert of the upper part at the projecting piston rod (7) is provided with externally flexibly spreadable spring elements (12, 13) engaging abutment means (16, 17) in the carrier (11) of the knob-like actuating element (2).
16. The pipetting device of one of claims 1 to 15, characterized in that the friction or slipping clutch (73) comprises groove-like indentations (65, 66) at an upper projecting cylindrical extension (64) of the intermediate element and inwardly directed blades (67, 68) at suspending rim portions of the cover cap.
17. The pipetting device of one of claims 8 to 16, characterized in that the teeth are defined to be blades to provide for a lateral yielding motion.
18. The pipetting device of one of claims 8 to 17, characterized in that the locking profiles (88-91) are defined to be at one side.
19. The pipetting device of one of claims 8 to 17 and 18, 19, characterized in that the roots of the teeth (92-94) are flexible.
20. The pipetting device of one of claims 8 to 19, characterized in that the profiles project from a gear ring and the other gear ring is provided with negative profiles.
21. The pipetting device of one of claims 8 to 20 and 18 to 21, characterized in that both gear rings are arranged on peripheral circles having different radii, wherein the beads of the respectively opposite detent means overlap each other and that a flexible yielding of the teeth, in particular a radial direction, is provided.
22. The pipetting device of one of claims 3 to 21, characterized in that the gear rings are defined with a teething and counter-teething in the manner of press buttons thus defining detent elements.

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