EP2415525B1 - Pipette for a pipette system with pipette and syringe - Google Patents

Description

The invention relates to a pipette for a pipette system with pipette and syringe, namely a pipette having the features of the preamble of claim 1.

Pipettes are devices for measuring and transferring liquids. In the present case is a pipette that allows a gradual release of a liquid wedge from a syringe (Repetierpipette). Such a pipette is for example from the DE 199 63 141 A1 and the EP 1 110 612 A1 known. In such a pipette, liquid is taken up in the syringe used in the pipette housing of the pipette in one go. Then the pipette is moved to the place of application. At the point of use, the liquid taken up in the syringe is released step by step by repeated actuation of the actuating lever located on the pipette housing in previously set portions. The repeating pipette known from practice (multiple dispensers "HandyStep", the BRAND GMBH + CO KG, Wertheim in the general catalog "GK800" from page 61) has a piston adjusting device in the form of a rack and pawl combination. The rack is made in one piece from an extremely dimensionally stable metal, especially brass, machined. The cost of producing such a rack is relatively high in relation to the cost of the pipette as part of a large-scale production.
Specifically, the teaching of the present invention is based on a pipette with a one-piece rack in such a piston adjusting device. From the EP 0 143 796 B1 Although it is a two-piece rack out, but on each section has a different teeth with different tasks on a rack member teeth in sawtooth shape is integrally formed. It can be assumed that this is also a metal rack whose teeth have been produced by machining processing on the actual rack carcass.
The teaching is based on the problem to optimize the known pipette with axially displaceable rack while maintaining the precision in terms of manufacturing costs in particular under aspects of mass production.

The above-indicated problem is in a pipette having the features of the preamble of claim 1 by the features of the characterizing part of claim 1 solved. Preferred embodiments and further developments are the subject of the dependent claims.

In the prior art, it is continuous so that the rack together with the teeth is made in one piece of metal highly dimensionally accurate. This is expensive and not optimal for a modern, highly effective mass production technology. According to the invention, the rack is now made in several parts, namely at least two parts, preferably exactly two parts. It consists first of a carrier which has a receptacle for a toothing part. In or on the receptacle of the carrier sits the toothing part, which in turn has the toothing of the rack.

The carrier on the one hand and the toothing part on the other hand can be made of different materials. The material of the carrier can be adapted to the local requirements. The carrier must be dimensionally stable and the toothed part fixed securely and in the correct position in the piston adjusting device. It does not have to be very dimensionally stable and it does not have to fulfill the special requirements for finely imaged toothing.

In contrast, the toothing part is highly dimensionally accurate to manufacture and must be highly precise executable especially in the teeth. This is usually a more expensive material to use. The outer shape of the toothing part, in particular what deflections or the like. does not have to be very precise, because here the carrier acts with its rigidity. The toothing part may in particular be made relatively thin. Its spatial orientation and fixation experience it only in connection with serving as a stiff backbone wearer.

Particularly preferred embodiments and further developments of the teaching according to the invention are the subject of the dependent claims.

For the choice of material of the toothing part, it is recommended in the first place that the toothing part consists of a high-quality, preferably fiber-reinforced plastic, in particular of a fiber-reinforced PEEK. Such a plastic part can be manufactured as a series part with high precision and excellent dimensional stability and low shrinkage. However, this toothing part is expediently made as small as possible in terms of volume, because the material used is relatively expensive. In this context, it is preferred that the Support made of steel, in particular stainless steel, or of a dimensionally stable plastic, preferably made of PPS exists.

The wearer can be quite voluminous and is designed so that it is as stiff as possible. Its dimensional accuracy in detail is less important. The material to be used here can be significantly cheaper than the material of the toothing part. Each of the two parts are assigned the tasks that best suit them.

In order to realize the optimal connection of the carrier with the toothing part, it is recommended that the toothing part has a longitudinal contour, which is adapted to a longitudinal counter contour on the carrier so that a positive, preferably axially straight guide results, wherein , Preferably, the contour and the mating contour are formed as a T-slot guide. By this guide, the flat and usually relatively thin toothing part is aligned.

The dimensional accuracy of the toothing part can be further improved by the fact that the toothed part seen in cross section has at least one longitudinal stiffening web on the side opposite the toothing. The filling behavior in the injection molding process in a plastic part is significantly smoother by such a bridge.

According to a preferred teaching, it is recommended that the toothing part including the toothing in cross section has a ratio of the width to the height greater than 1.5, preferably greater than 4.0. Over its length, such a relatively uniformly elongate toothing part hardly has a delay and only a relatively small deflection. Due to the low height in relation to the width, it can be aligned relatively easily when inserted into the carrier. The toothing part can thus be optimized for the dimensional accuracy of the tooth pitch of the toothing, the deflection over the entire length of the toothing part may have less importance.

The teaching of the invention is of particular importance with a relatively small tooth pitch, tooth pitches below 1 mm can be produced in metal racks only with great effort. In a high-quality plastic injection molding technique can be according to the teachings of the invention, smaller tooth pitches to reach. Accordingly, it is recommended according to preferred teaching that the toothing has a pitch of less than 1.0 mm, preferably less than 0.6 mm. It is obvious that a smaller pitch allows a greater number of steps and possible sub-volumes.

The toothing in the case of the pipette according to the invention can also be optimized in the tooth form and in the tooth height. It is recommended that the toothing is sawtooth-shaped and the tooth angle between the tooth back and the tooth flank is between 25 ° and 45 °.

At a low pitch of, for example, 0.6 mm, the teeth are very fine on both the gearing and the pawl. In particular, in this case, it may be recommended that the pawl, which preferably consists of fiber-reinforced plastic, having a plurality of ratchet teeth, preferably three ratchet teeth.

In a preferred constructive embodiment of a typical pipette of the type in question, it is recommended that the width of the pawl is greater than 4 mm, preferably greater than 5.5 mm.

Furthermore, it may be recommended that the ratchet teeth of the pawl have the sawtooth shape of the toothing and that, preferably, the pitch of the ratchet teeth is less than the pitch of the toothing. The ratchet teeth so fall even with appropriate inclination of the pawl in the teeth on the toothing part and achieve a safe, force-transmitting engagement.

Already in the prior art, a rigidly arranged stop is present on the pipette housing, which limits the movement of the pawl in the direction of the syringe. Such a construction is also recommended in the case of the pipette according to the invention. Furthermore, it is recommended that the toothing part has a stroke stop for the absorption of liquid in the syringe. The stroke stop ensures dimensional accuracy when engaging the first stroke to dispense liquid after previously taking up liquid in the syringe.

If the still possible last discharge stroke is smaller than the stroke set by means of the volume setting device, then the last possible delivery stroke should be prevented in order to avoid volume errors. For this purpose, it is recommended that the rack has a cam which cooperates with the spool and with the piston advanced into the syringe raises the spool so that the pawl is dug out of the gearing. To be able to set this residual stroke prevention and to create a tolerance compensation, it is recommended that the cam is mounted on the rack in the axial direction adjustable.

For the adjustment of the cam on the rack in the axial direction, there are various possibilities. A particularly preferred construction is that the cam is mounted in an adjustable manner in the axial direction on a sliding guide arranged on the carrier of the rack. It is particularly useful in this case then that the carrier of the rack is designed in one piece with this sliding guide.

Incidentally, the piston adjusting device typically has a receptacle for a piston head of a syringe. It is particularly useful then that the carrier of the rack is made in one piece with this recording

If both previously described aspects come together, then the carrier of the rack at the lower end is made in one piece with the receptacle of the piston adjusting device and integrally formed at the upper end in one piece with the sliding guide for the cam.

Fig. 1

eine perspektivische Darstellung einer bekannten Pipette mit eingesetzter Spritze,

Fig. 2

im Längsschnitt, ausschnittweise im Bereich des Betätigungshebels, ein bevorzugtes Ausführungsbeispiel einer Pipette gemäß der Erfindung,

Fig. 3

in einem Fig. 2 ähnlichen Längsschnitt, die Pipette mit teilweise betätigtem Betätigungshebel und Klinke im Eingriff in die Zahnstange,

Fig. 4

in einem Fig. 2 ähnlichen Längsschnitt, die Pipette mit Betätigungshebel in Endstellung,

Fig. 5

in einem Fig. 2 ähnlichen Längsschnitt, die Pipette mit vorgeschobener Zahnstange und ausgehobener Klinke,

Fig. 6

in einem Fig. 2 ähnlichen Längsschnitt, die Pipette in einer Variante mit einer verstellbaren Nocke,

Fig. 7

in einem Fig. 2 ähnlichen Längsschnitt, die Pipette in einer weiteren Variante mit einer verstellbaren Nocke,

Fig. 8

im Querschnitt, ausschnittweise im Bereich der Zahnstange, ein bevorzugtes Ausführungsbeispiel einer Pipette gemäß der Erfindung,

Fig. 9

Detailansichten eines bevorzugten Ausführungsbeispiels einer Zahnstange einer Pipette gemäß der Erfindung,

Fig. 10

eine perspektivische Darstellung einer Baugruppe einer Pipette mit eingesetzter Spritze und

Fig. 11

eine perspektivische Darstellung einer Zahnstange eines bevorzugten Ausführungsbeispiels einer Pipette gemäß der Erfindung.

In the following, the invention will now be explained in more detail with reference to a drawing showing merely exemplary embodiments. In the drawings, the figures show the following:

Fig. 1

a perspective view of a known pipette with inserted syringe,

Fig. 2

in a longitudinal section, in sections in the region of the actuating lever, a preferred embodiment of a pipette according to the invention,

Fig. 3

in one Fig. 2 similar longitudinal section, the pipette with partially actuated lever and pawl in the rack,

Fig. 4

in one Fig. 2 similar longitudinal section, the pipette with actuating lever in the end position,

Fig. 5

in one Fig. 2 similar longitudinal section, the pipette with advanced rack and raised latch,

Fig. 6

in one Fig. 2 similar longitudinal section, the pipette in a variant with an adjustable cam,

Fig. 7

in one Fig. 2 similar longitudinal section, the pipette in another variant with an adjustable cam,

Fig. 8

in cross-section, in sections in the region of the rack, a preferred embodiment of a pipette according to the invention,

Fig. 9

Detailed views of a preferred embodiment of a rack of a pipette according to the invention,

Fig. 10

a perspective view of an assembly of a pipette with inserted syringe and

Fig. 11

a perspective view of a rack of a preferred embodiment of a pipette according to the invention.

Fig. 1 shows the basic design of a pipette 1 according to the invention with an inserted syringe 2. The syringe 2 has a cylinder 2.1 with a mounting portion 2.2, which is preferably designed as a flange, and with a piston which in Fig. 1 can not be seen because it is located in the pipette housing 3 of the pipette 1 shown there. The piston has a piston which is also pushed completely out of the cylinder 2.1 and out of this cylinder 2.1 on the end of the piston head 2.3. The pipette housing 3 defines a longitudinal axis which is coaxial with the rotationally symmetrical syringe (2).

One recognizes in Fig. 1 how the syringe 2 to be handled with the pipette 1 with its attachment section 2.2 and the piston head 2.3 is inserted into the pipette housing 3. The prior art knows here a radial coupling (so in Fig. 1 shown; see also DE 199 63 141 A1 ) and an axial coupling (see, eg DE 199 17 907 A1 ). In the teaching of the present invention, this distinction does not matter.

In Fig. 1 is indicated that in the pipette housing 3 in the direction of the longitudinal axis of the pipette housing 3, that is, axially displaceable piston adjusting device 4 for the piston head 2.3 of the syringe 2 is located. The piston adjusting device 4 is actuated by means of a movable in the pipette housing 3 and partially protruding from the pipette housing 3 for the purpose of manual operation operating lever 5.

On the pipette housing 3, a handle part 3.1 and a finger strap 3.2 are formed. If you hold the pipette housing 3 on the handle part 3.1 with the palm, so you can press the operating lever 5 with your thumb, ie in Fig. 1 Press down towards the syringe (2). Each actuation of the operating lever 5 has the delivery of a specific, precisely set amount of the previously recorded in the syringe 2 liquid (repetitive pipette). To adjust the volume delivered by each actuation of the actuating lever 5, a volume setting device 6 is provided on the pipette housing 3. This adjustment is known per se from the prior art and is realized in a similar manner also in the case of the pipette forming the starting point.

For the further features of the pipette according to the invention, reference must now be made to the additional figures.

The piston adjusting device 4 initially has an axially displaceably arranged in the pipette housing 3, with the piston head 2.3 of an inserted syringe 2 coupled rack 7, which with a toothing 7.1 (Fig. 8 and 9 Is provided on the operating lever 5 is a pivotally mounted pawl 8 of the piston adjusting device 4, which engages upon actuation of the actuating lever 5 in the opposing toothing 7.1 of the rack 7, as can be seen from the episode of Fig. 2 to 4 good to take. If the actuating lever 5 is actuated, the piston of the syringe 2 is displaced by this engagement via the piston head 2.3, regularly downwards into the cylinder 2.1, for the purpose of dispensing a certain set amount of liquid.

On the rack 7 is a spool 9, the in FIGS. 2 and 3 is particularly clear. He is executed here as a double-folded bent part. This control slide 9 holds the pawl when the actuating lever 5 is not actuated (FIG. Fig. 2 ) About the teeth 7.1 of the rack 7. This spool 9 is adjustable in its position on the rack 7, what it just the volume setting 6 there. Other embodiments of the spool 9 are known, which basically control the engagement of the pawl 8 in the toothing 7.

If the operating lever 5 is actuated, it moves from the in Fig. 2 shown position to the left. The down to the teeth 7.1 biased by spring force pawl 8 leaves the spool 9, now applies to the teeth 7.1 and engages in this ( Fig. 3 ). The further movement of the actuating lever 5 now leads to a movement of the rack 7 in Fig. 3 to the left in the Fig. 4 shown position, the end of the actuating stroke. If you let go now the operating lever 5 again, so he moves himself under spring force back into the in Fig. 2 shown position back. The next actuation stroke can begin.

8 and 9 Now show the essential essence of the teaching of the invention, namely that the rack 7 is made of several parts and at least a support 7.2 and a toothing part 7.3, wherein the carrier 7.2 has a receptacle for the toothing part 7.3 and the toothing part 7.3 carries the toothing 7.1. The carrier 7.2 on the one hand and the toothing part 7.3. On the other hand, they are made of different materials, which can meet the respective requirements particularly well. This has the advantages already explained in detail in the general part of the description.

Normally, the rack 7 will be made in two parts. In principle, however, other parts may belong to the rack 7. Essential is the special task assignment to the carrier 7.2 on the one hand and to the physically separate from the carrier, but connected to it gearing part 7.3, which carries the gearing 7.1 on the other. According to the invention therefore no one-piece design of the rack 7 is provided, but a multi-part design.

It is particularly preferred that the toothing part 7, 3 consists of a high-strength material, which can be manufactured dimensionally accurate and with minimal shrinkage, and that the carrier 7.2 consists of a material that is more cost-effective compared to the material of the toothing part 7.3, which less good dimensionally accurate to manufacture.

In the illustrated and preferred embodiment already shows the hatching in 8 and 9 in that here the toothing part 7.3 is made of a high quality, preferably fiber reinforced plastic, in particular of a fiber reinforced PEEK, consists. Furthermore, it can be seen that here the carrier 7.2 made of steel, in particular stainless steel, or of a dimensionally stable plastic, preferably of PPS exists

Thus, a combination of fiber-reinforced PEEK for the toothing part 7.3 with dimensionally stable PPS for the carrier 7.2 is particularly preferred.

A particularly preferred mechanical construction of the pipette according to the invention also results 8 and 9 , It can be seen here that the toothing part 7.3 has a longitudinal contour 7.4, which is adapted to a longitudinally extending counter contour 7.5 on the carrier 7.2 in such a way that a form-fitting, axially straight guide results. Here and preferably, the contour 7.4 and the mating contour 7.5 are formed as a T-slot guide. The T-slot guide can be in Fig. 8 recognize very well.

In order to optimize the filling behavior in the injection molding process for an existing plastic toothing part 7.3 and thereby increase the dimensional stability, in particular in the area of the toothing 7.1 is in in Fig. 8 illustrated embodiment, that the toothing part 7.3 in cross-section at least one longitudinal stiffening web 7.6 relative to the toothing 7.1. More specifically, here are four equally spaced stiffening ribs 7.6.

Also off Fig. 8 can be the profiling of the toothing part 7.3 refer. Here, it is provided that the toothing part 7.3 including the toothing 7.1 in cross section has a ratio of the width 7.7 to the height 7.8 including the toothing 7.1 greater than 1.5, preferably greater than 4.0. In the illustrated and preferred embodiment, a ratio of the width of 7.7 to the height 7.8, which is measured to the top of the teeth 7.1, resulting from a little more than 4. It can be seen that the outer contour of the toothing part 7.3 is basically rectangular, although with a two-sided stage of the T-slot guide because of running.

The illustrated and preferred embodiment shows for the teeth 7.1 a very fine pitch, in particular one of less than 1 mm, preferably less than 0.6 mm. This one looks especially good in Fig. 9 , It recognizes one that the teeth 7.1 is designed sawtooth-shaped and the tooth angle 7.10 between the tooth back and the tooth flank is between 25 ° and 45 °. One can see here, despite the fineness of the division 7.9 sufficient tooth height, which allows a safe engagement of the ratchet teeth of the pawl 8,

This brings us to another special feature of the construction according to the invention. Here it is namely provided that the pawl 8, which preferably consists of fiber-reinforced plastic, has a plurality of ratchet teeth, preferably three ratchet teeth. The three ratchet teeth provided here ensure a secure engagement of the pawl 8 in the fine toothing 7.1. According to a particularly preferred teaching is so far provided that the ratchet teeth of the pawl 8 have the sawtooth shape of the teeth 7.1 and the pitch of the ratchet teeth is less than the pitch of the teeth 7.1. This takes into account the peculiarity of the construction according to the invention with the pivotally mounted with the actuating lever 5 pivot bearing of the pawl 8 ( Fig. 2 to 4 ). Even with this arcuate displacement, the ratchet teeth fall securely into the toothing 7.1, because they have a slightly different pitch with respect to the toothing 7.1.

This in Fig. 8 illustrated and so far preferred embodiment shows a construction in which the width of the pawl 8 is greater than 4 mm, preferably greater than 5.5 mm. Ultimately, the width of the pawl 8 also depends on the lifting force to be transmitted, which then has to be introduced over the width into the toothing part 7.3 and thus into the rack 7 with a particularly fine pitch of the toothing 7.1. Considering that here Hubkräfte between 5 and 25 N must be transmitted, so you have to accept an acceptable width of the pawl 8 in purchasing. Overall, the carrier 7.2 has a total width which is about 1.5 times to 2 times the width of the pawl 8.

In Fig. 2 and 4 and in Fig. 9 is shown that in the illustrated embodiment, but this is known per se, a fixedly positioned stop 10 is provided which limits the movement of the pawl 8 in the direction of the syringe 2. This has the meaning explained in the general part of the description. The stop 10 may be assigned to the actuating lever 5 instead of the pawl 8 also directly. It is fixedly attached to the pipette housing 3. You can see in Fig. 9 the pawl 8 are immediately in front of the stop 10.

Already in the general part of the description, it has been pointed out that the dimensional stability during the first stroke after the previous suction of liquid into the syringe 2 is ensured by a further stop, namely a stroke stop 7.11 on the toothing part 7.3. This one recognizes in Fig. 9 Left. It interacts with the stop 10 on the pipette housing 3.

Furthermore, in the general part of the description, the problem of Resthubverhinderung has been addressed in the last discharge stroke by operating the operating lever 5. Here is provided according to the invention according to the preferred teaching that the rack 7 has a cam 7.12, which cooperates with the spool 9 and raises in the syringe 2 advanced piston the spool 9, so that the pawl 8 is excavated from the teeth 7.1.

The stop given by the cam 7.12 can be seen in Fig. 5 to 7 in different variants. In the embodiment of Fig. 2 to 5 the cam 7.12 is integrally formed on the carrier 7.2. In the embodiments of 6 and 7 on the other hand, the cam 7.12 on the rack 7, more precisely on the support 7.2, mounted adjustably in the axial direction, to make an adjustment and tolerance compensation here. In any case, the cam 7.12 acts so that the spool 9 is raised and with the pawl 8 lifts up and triggers their ratchet teeth from the gearing 7.1 on the gearing part 7.3. The pawl 8 then moves in idle. It has, to make this possible, even a raised contact surface 8.1, with which it rests on the spool 9.

In Fig. 10 is that assembly of the pipette 1 is shown, which is driven with the exception of the cylinder 2.1 of the syringe 2 during the actuating stroke. The piston adjusting device 4 may, for. B. be constructed as in the DE 20 2010 009 747 U1 disclosed. It has at least one coupling for the piston head 2.3 and a button for its operation. This can also be used to move the piston with the piston head 2.3 in the syringe 2 and the rack 7 in the pipette housing 3.

As Fig. 11 shows, here has the coupling of the piston adjusting device 4 a receptacle 4.1, which is connected directly or indirectly with the piston head 2.3 in the pipette housing 3 when attaching the syringe 2. In Fig. 11 is an advantageous Embodiment shown, in which the recording 4.1 with the carrier 7.2 of the rack 7 is made in one piece. In practice, for example, the carrier 7.2 of the rack 7 with the receptacle 4.1 of the piston adjusting device 4 may be designed as a one-piece injection-molded part made of plastic.

In Fig. 10 can be seen right behind the end of the carrier 7.2 of the rack 7, the aforementioned cam 7.12. This is plugged here on a sliding guide 7.13 and mounted adjustable on this in the axial direction. The cam 7.12 will be on the in Fig. 11 mounted on the top right sliding guide 7.13 and then brought into the axial position, which is to be provided for them. In this position, it is fixed on the sliding guide 7.13, for example by a fixing screw. Fig. 11 shows right above the sliding guide 7.13 for the cam 7.12. It can be seen here that the carrier 7.2 in this exemplary embodiment is also designed in one piece with this displacement guide 7.13. Again, it may be the one-piece molding in the form of an injection molded part.

This in Fig. 11 illustrated embodiment, therefore, the carrier 7.2 with the receptacle 4.1 integrally formed at one end and the sliding guide 7.13 integrally executed at the other end.

In Fig. 11 is finally the one above in connection with 8 and 9 already mentioned, longitudinal counter contour 7.5 shown on the carrier 7.2. It can be seen that the mating contour 7.5 is here arranged segmentally, in sections.

LIST OF REFERENCE NUMBERS

1

pipette

2

syringe

2.1

cylinder

2.2

attachment section

2.3

piston head

3

pipette housing

3.1

Handle part

3.2

finger rest

4

Piston setting device

4.1

exception

5

actuating lever

6

Volumeneinstelleinrichtung

7

rack

7.1

gearing

7.2

carrier

7.3

toothed piece

7.4

contour

7.5

mating contour

7.6

reinforcing web

7.7

width

7.8

height

7.9

division

7.10

tooth angle

7.11

stroke stop

7.12

cam

7.13

displacement guide

8th

pawl

8.1

contact surface

9

spool

10

attack

Claims (14)

1. Pipette
   for a pipette system comprising a pipette (1) and a syringe (2),
   in the case of which the syringe (2) has a cylinder (2.1), with a fastening portion (2.2) designed preferably in the form of a flange, and a plunger, which has a plunger head (2.3) which, even when the plunger is pushed all the way into the cylinder (2.1), projects out of the end of the cylinder (2.1),
   having a pipette housing (3) which has a longitudinal axis, wherein a syringe (2), which is to be operated by the pipette (1), can be inserted into the pipette housing (3), and removed from the same, by way of its fastening portion (2.2) and plunger head (2.3),
   having a plunger-adjusting device (4) for the plunger head (2.3) of the syringe (2), it being possible for said plunger-adjusting device to be displaced in the pipette housing (3) in the direction of the longitudinal axis of the latter, i.e. axially,
   having an actuating lever (5) for actuating the plunger-adjusting device (4), said actuating lever being mounted in a movable manner in the pipette housing (3) and projecting part of the way out of said pipette housing,
   preferably having a volume-adjusting device (6) for adjusting the liquid volume which is pipetted when the actuating lever (5) is actuated, said volume-adjusting device being arranged in the pipette housing (3), wherein the plunger-adjusting device (4) has a rack (7) with a toothing formation (7.1), said rack being arranged in an axially displaceable manner in the pipette housing (3) and being coupled to the plunger head (2.3) of an inserted syringe (2),
   the actuating lever (5) has arranged on it a pivotably mounted catch (8) which, when the actuating lever (5) is actuated, engages in the toothing formation (7.1) of the rack (7) and displaces the plunger of the syringe (2) via the plunger head (2.3), and
   the rack (7) has arranged on it a control slide (9) which controls the engagement of the catch (8) in the toothing formation (7.1) and which can be adjusted in position on the rack (7), preferably, via the volume-adjusting device (6),
   characterized
   in that the rack (7) is designed in more than one piece and comprises at least a carrier (7.2) and a toothing-formation part (7.3), wherein the carrier (7.2) has a mount for the toothing-formation part (7.3) and the toothing-formation part (7.3) carries the toothing formation (7.1), and
   in that the carrier (7.2), on the one hand, and the toothing-formation part (7.3), on the other hand, consist of different materials.
2. Pipette according to Claim 1, characterized
   in that the toothing-formation part (7.3) consists of a preferably fibre-reinforced plastic material, in particular of a fibre-reinforced PEEK, and
   in that the carrier (7.2) consists of steel, in particular of stainless steel, or of a dimensionally stable plastic material, preferably of PPS.
3. Pipette according to either of the preceding claims, characterized
   in that the toothing-formation part (7.3) has a longitudinally running contour (7.4), which is adapted to a longitudinally running mating contour (7.5) on the carrier (7.2) such that a form-fitting, preferably axially rectilinear guide is formed, wherein, preferably, the contour (7.4) and the mating contour (7.5) are designed in the form of a T-groove guide.
4. Pipette according to one of the preceding claims, characterized
   in that, as seen in cross section, the toothing-formation part (7.3) has at least one longitudinally running adjustment crosspiece (7.6) on the side located opposite the toothing formation (7.1).
5. Pipette according to one of the preceding claims, characterized
   in that, as seen in cross section, the toothing-formation part (7.3) including the toothing formation (7.1) has a ratio of width (7.7) to height (7.8) of greater than 1.5, preferably greater than 4.0.
6. Pipette according to one of the preceding claims, characterized
   in that the toothing formation (7.1) has a pitch (7.9) of less than 1.0 mm, preferably of less than 0.6 mm.
7. Pipette according to one of the preceding claims, characterized
   in that the toothing formation (7.1) is of sawtooth-shaped design and the tooth angle (7.10) between the back of each tooth and the tooth flank is between 25° and 45°.
8. Pipette according to one of the preceding claims, characterized
   in that the catch (8), which consists preferably of fibre-reinforced plastic material, has a plurality of, preferably three, catch teeth, and/or
   in that the width of the catch (8) is greater than 4 mm, preferably greater than 5.5 mm.
9. Pipette according to Claim 8, characterized
   in that the teeth of the catch (8) have the sawtooth shape of the toothing formation (7.1), and in that, preferably, the pitch of the catch teeth is smaller than the pitch of the toothing formation (7.1).
10. Pipette according to one of the preceding claims, characterized
    in that a stop (10) is arranged at a fixed location on the pipette housing (3) and limits the movement of the catch (8) or of the actuating lever (5) in the direction of the syringe (2).
11. Pipette according to one of the preceding claims, characterized
    in that the toothing-formation part (7.3) has a displacement stop (7.11) for the operation of taking liquid into the syringe (2).
12. Pipette according to one of the preceding claims, characterized
    in that the rack (7) has a protuberance (7.12), which interacts with the control slide (9) and, when the plunger is advanced into the syringe (2), raises the control slide (9) so that the catch (8) is raised out of the toothing formation (7.1).
13. Pipette according to Claim 12, characterized
    in that the protuberance (7.12) is fitted in an axially adjustable manner on the rack (7).
14. Pipette according to one of the preceding claims, characterized
    in that the protuberance (7.12) is fitted in an axially adjustable manner on a displacement guide (7.13), which is arranged on the carrier (7.2) of the rack (7), and in that the carrier (7.2) of the rack (7) is designed in one piece with the displacement guide (7.13), and/or in that the plunger-adjusting device (4) has a mount (4.1) for a plunger head (2.3) of a syringe (2), and in that the carrier (7.2) of the rack (7) is designed in one piece with the mount (4.1).

Images