EP3442709B1 - Pipette for withdrawing an extended range of volumes of liquid - Google Patents

Description

TECHNICAL AREA

The invention relates to the field of sampling pipettes, also called laboratory pipettes or liquid transfer pipettes, intended for the sampling and dispensing of liquid in containers or the like.

The pipettes concerned by the present invention are manual pipettes and motorized pipettes. These pipettes are intended to be held in the hand by an operator, during the operations of sampling and dispensing of liquid. For manual pipettes, these operations are carried out by setting in motion a pipetting control button, obtained by applying an actuating pressure on this same button which is mechanically transferred to a control rod. On motorized pipettes, the pressure of the operator on the control button generates a signal which is transmitted to the control unit of the pipette, so that the latter triggers the setting in motion of the control rod through a suitable motor on board the pipette.

It is noted that in the manual pipettes concerned by the present invention may have an electronic counter and / or display, the pipette then having a “hybrid” character since it combines both a mechanical aspect and an electronic aspect.

STATE OF THE PRIOR ART

For many years, the design of the sampling pipettes has been the subject of numerous improvements, essentially aimed at simplifying the design of the pipettes, or even at enhancing their ergonomics.

Usually, to benefit from acceptable accuracy, the range of volumes that can be withdrawn by a pipette is between approximately 10% of the nominal volume, and 100% of this nominal volume corresponding to the maximum volume that the pipette can withdraw.

• une première pipette d'un volume nominal de 30 µl, pouvant être utilisée sur une plage de volumes allant de 3 à 30 µl ;
• une seconde pipette d'un volume nominal de 300 µl, pouvant être utilisée sur une plage de volumes allant de 30 à 300 µl ; et
• une troisième pipette d'un volume nominal de 1250 µl, pouvant être utilisée sur une plage de volumes allant de 300 à 1250 µl.

Consequently, when an operator has to pipette different samples spanning a wide range, these operations require the use of several pipettes. For example, when a series of operations requires the pipetting of volumes falling within a range from 3 to 1250 μl, the following three pipettes may be required:

• a first pipette with a nominal volume of 30 µl, which can be used over a range of volumes from 3 to 30 µl;
• a second pipette with a nominal volume of 300 µl, which can be used over a range of volumes from 30 to 300 µl; and
• a third pipette with a nominal volume of 1250 µl, which can be used over a range of volumes from 300 to 1250 µl.

In this situation, the plurality of pipettes guarantees performance of precision and accuracy, but it does, however, clutter the bench. Requirement FR3019895 is also part of the state of the prior art.

STATEMENT OF THE INVENTION

The invention therefore aims to respond at least partially to the drawback identified above.

• corps de pipette ;
• une tige de commande déplaçable en translation relativement au corps de pipette, selon un axe longitudinal de la pipette ; et
• une chambre d'aspiration.

To do this, the invention relates to a sampling pipette comprising:

• pipette body;
• a control rod movable in translation relative to the pipette body, along a longitudinal axis of the pipette; and
• a suction chamber.

• un ensemble de N pistons concentriques, N correspondant à un entier supérieur ou égal à deux, chacun des pistons participant à la délimitation de ladite chambre d'aspiration ; et
• un module d'accouplement de la tige de commande avec l'ensemble de N pistons concentriques, ledit module étant configuré de manière à pouvoir être amené dans N configurations distinctes dans lesquelles il assure respectivement l'accouplement de la tige de commande avec 1, 2,..., N pistons.

According to the invention, the pipette also comprises:

• a set of N concentric pistons, N corresponding to an integer greater than or equal to two, each of the pistons participating in the delimitation of said suction chamber; and
• a control rod coupling module with the set of N concentric pistons, said module being configured so as to be able to be brought into N distinct configurations in which it ensures respectively the coupling of the control rod with 1, 2 , ..., N pistons.

The invention is thus remarkable in that it makes it possible to extend the range of volumes that can be withdrawn, by implanting several pistons within the pipette as well as a module for coupling the control rod with each of these pistons. . Consequently, during a pipetting operation, the number of pistons in operation is a function of the volume to be withdrawn.

This solution has the advantage of reducing the number of pipettes required when the pipetting operations require the sampling of various volumes, and this without affecting the accuracy and precision performance of the pipette. This advantageously results in a saving of space on the bench. In addition, by replacing several pipettes with a single pipette, this offers a possibility of traceability of a protocol by recording all the pipettings carried out with this same pipette.

In addition, the pipette according to the invention has a reduced bulk, thanks to the concentric arrangement of its pistons.

The invention furthermore presents at least any one of the following optional characteristics, taken individually or in combination.

• que le module d'accouplement comprend au moins un doigt d'accrochage de piston s'étendant radialement relativement à l'axe longitudinal de pipette,
• qu'au moins N-1 pistons présentent chacun une fente d'accrochage orientée et ouverte circonférentiellement, les fentes présentant des longueurs circonférentielles différentes pour chacun desdits au moins N-1 pistons,
• et que ladite pipette est configurée de manière à ce que le doigt d'accrochage puisse être déplacé circonférentiellement dans et en dehors des fentes situées en regard radialement les unes des autres.

It is provided :

• that the coupling module comprises at least one plunger catch extending radially relative to the longitudinal axis of the pipette,
• that at least N-1 pistons each have a hooking slot oriented and open circumferentially, the slots having different circumferential lengths for each of said at least N-1 pistons,
• and that said pipette is configured so that the gripping finger can be moved circumferentially in and out of the slots located facing each other radially.

In other words, the coupling / uncoupling of each piston with the control rod is effected by a bayonet type connection, with the finger constituting the lug of this connection. Thanks to the inventive design which has been developed, the number of pistons coupled to the control rod simply depends on the relative angular position between the finger and the slots located facing each other radially. This angular relative position can be obtained manually by the operator using an appropriate control member positioned on the pipette, or even more preferably, automatically by means of motorized means controlled by a pipette control unit. .

However, the coupling module can take any other form deemed appropriate, without departing from the scope of the invention. As an example, this module can be based on a mechanical, magnetic grip, etc.

The coupling module comprises a rotary coupling member equipped at its lower end with said finger, and rotatably mounted at its upper end on the control rod, along the longitudinal axis of the pipette.

The rotary coupling member is preferably produced using two parts mounted to slide relative to each other, along the longitudinal axis of the pipette, a deployment spring being arranged between these two parts so to generate an effort tending to separate them from each other.

The coupling module comprises an extension of the control rod integral in translation with the control rod, and said two parts of the rotary coupling member are respectively formed by a high part and a low part, the latter being mounted mobile. in translation along the longitudinal axis, relative to the control rod extension.

The coupling module further comprises a movement transformation body cooperating with the rotary coupling member so that a relative translational movement between them two along the longitudinal axis, simultaneously leads to a relative rotation between them two , also along the longitudinal axis. In other words, the cooperation between the movement transforming body and the rotary coupling member causes the latter to move helically.

Preferably, the movement transformation body comprises at least a first helical ramp as well as at least a second helical ramp, and the rotary coupling member is equipped with a follower roller which, when it cooperates with the first ramp makes it possible to cause the rotation of the rotary coupling member in a first direction of rotation, and which, when it cooperates with the second ramp makes it possible to cause the rotation of the rotary coupling member in a second direction of rotation. This design makes it possible to obtain the coupling and uncoupling of the pistons in a simple and reliable manner.

The sampling pipette is preferably designed so that the rotation of the rotary coupling member according to the first direction of rotation is obtained by a first downward overtravel of the control rod from an end of travel position purge thereof, and the rotation of the rotary coupling member according to the second direction of rotation is obtained by a second overtravel upward of the control rod from a high position of pipetting of this rod control. Thus, the pipette is designed to obtain the coupling and uncoupling of the pistons by simple translations of the control rod, in overtravel going respectively beyond the purge stroke and back from the high pipetting position. One of the advantages linked to this specificity resides in the simplicity of design of the pipette, since it is the same control rod, in a movement according to the same degree of freedom of translation, which allows alternately to perform the pipetting operations and the coupling and uncoupling operations of the pistons.

Preferably, the first overtravel takes place against a force generated by a first centering spring tending to push the rotary coupling member upwards relative to the movement transforming body, and the second overtravel s 'performs against a force generated by a second centering spring tending to push the rotary coupling member down relative to the movement transforming body.

Preferably, the pipette is configured so that the movement of the control rod is carried out manually or motorized, as indicated previously. In this regard, it is noted that hybrid pipettes also fall within the protective field of the invention.

Preferably, the number N of pistons is greater than or equal to three, but a solution with two concentric pistons is also possible, without departing from the scope of the invention.

The sampling pipette is preferably designed so as to be able to withdraw a range of volumes ranging from 0.5 to 1250 μl, or designed so as to be able to withdraw a range of volumes ranging from 500 to 10000 μl.

The innermost piston is permanently attached to the coupling module. Alternatively, it could also be coupled and uncoupled to the control rod, via the coupling module. According to yet another alternative, it is the outermost piston which could be permanently attached to the coupling module.

The pipette comprises a control member for adjusting the volume to be sampled, of the button, wheel, or other conventional form.

Finally, it is noted that the sampling pipette can be a single-channel or multi-channel pipette.

Other advantages and characteristics of the invention will appear in the detailed non-limiting description below.

BRIEF DESCRIPTION OF THE DRAWINGS

• la figure 1 représente une vue de face d'une pipette de prélèvement motorisée selon un mode de réalisation préféré de la présente invention ;
• la figure 2 est une vue en coupe axiale d'une partie basse de la pipette montrée sur la figure précédente ;
• la figure 3 est une vue en perspective d'un module d'accouplement de pistons mis en œuvre dans la pipette montrée sur les figures précédentes ;
• la figure 4 est en coupe axiale de la figure précédente ;
• la figure 5 est en vue en coupe prise selon la ligne V-V de la figure précédente ;
• la figure 6 est une vue en perspective d'une partie basse du module d'accouplement montré sur les figures 3 et 4, coopérant avec les pistons de la pipette ;
• les figures 7a à 7c schématisent des opérations de pipetage avec le module d'accouplement en première configuration ;
• les figures 8a à 8c schématisent des opérations de pipetage avec le module d'accouplement en seconde configuration ;
• les figures 9a à 9c schématisent des opérations de pipetage avec le module d'accouplement en troisième configuration ;
• les figures 10a à 11b schématisent le passage de la première à la seconde configuration du module d'accouplement ;
• les figures 12 à 13b schématisent le passage de la seconde à la troisième configuration du module d'accouplement ;
• les figures 14a à 15b schématisent le passage de la troisième à la seconde configuration du module d'accouplement ; et
• les figures 16a à 17b schématisent le passage de la seconde à la première configuration du module d'accouplement.

This description will be made with reference to the accompanying drawings, among which;

• the figure 1 shows a front view of a motorized sampling pipette according to a preferred embodiment of the present invention;
• the figure 2 is an axial section view of a lower part of the pipette shown in the previous figure;
• the figure 3 is a perspective view of a piston coupling module implemented in the pipette shown in the preceding figures;
• the figure 4 is in axial section of the previous figure;
• the figure 5 is in section view taken along line VV of the previous figure;
• the figure 6 is a perspective view of a lower part of the coupling module shown on the figures 3 and 4 , cooperating with the pistons of the pipette;
• the Figures 7a to 7c schematize pipetting operations with the coupling module in the first configuration;
• the Figures 8a to 8c schematize pipetting operations with the coupling module in second configuration;
• the Figures 9a to 9c schematize pipetting operations with the coupling module in the third configuration;
• the figures 10a to 11b schematize the transition from the first to the second configuration of the coupling module;
• the figures 12 to 13b schematize the transition from the second to the third configuration of the coupling module;
• the Figures 14a to 15b schematize the transition from the third to the second configuration of the coupling module; and
• the Figures 16a to 17b show the transition from the second to the first configuration of the coupling module.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring first to Figures 1 to 5 , a motorized sampling pipette 1 is shown according to a preferred embodiment of the invention.

Conventionally, this motorized pipette 1 is intended to be held by the hand of an operator, who, using his thumb, is capable of actuating a control button of the pipette to generate the dispensation of a liquid that has been previously aspirated.

More precisely, the single-channel pipette 1 comprises a handle 6 forming the upper body of the pipette, and above which is the pipetting control button 3, the upper part of which is intended to be subjected to the pressure of the operator's thumb . As an indication, it is noted that an electronic display screen 4 is provided on the handle 6, as well as control members 8 such as buttons or knobs, and in particular a control member for adjusting the volume to be sampled.

The upper part of the pipette is also equipped with an electronic control unit 10 and a motor 11, the latter preferably being direct current and controlled by the unit 10.

The output shaft 13 of the motor 11 is mechanically coupled to a device 15 for translating a control rod 12 of the pipette, along a longitudinal axis of the pipette 9 also corresponding to the longitudinal direction of the latter. It is noted that most of the constituent elements of the pipette are of revolutionary shapes, and centered on this axis 9.

Under the handle 6, the pipette 1 has a removable lower part 14, which ends downwards by a cone-holder tip 16 receiving a consumable 18, also called the sampling cone.

A cone ejector 20 opens downward from the handle 6. Conventionally, the ejector 20 can be set in motion relative to the handle 6 and the lower part 14, both forming a fixed body 22 of the pipette.

One of the features of the invention resides in the fact that the pipette is equipped with several concentric pistons, here three pistons referenced 24a, 24b, 24c. The number N of pistons could nevertheless be greater than or less than 3, without departing from the scope of the invention.

The three pistons are housed in the lower part 14, and centered on the longitudinal axis 9. The first piston 24a, located inside, has a cylindrical section of circular shape. The second piston 24b has an annular cross section, surrounding the first piston 24. The upper end 24b 'of the second piston 24b defines an axial housing 26 open upwards, the bottom of which is fitted with an O-ring 28 through which the first piston 24a. However, in the main part of the second piston 24b, a slight radial clearance is provided between the two pistons 24a, 24b, so that air can enter it. It is indicated that throughout the description, the terms “up” and “down” are to be considered in relation to the pipette held in the operator's hand, with a orientation such as that adopted during pipetting operations, that is to say with the control button 3 oriented upwards.

Similarly to that set out above, the upper end 24c ′ of the third piston 24c defines an axial housing 30 open upwards, the bottom of which is fitted with an O-ring 32 crossed by the second piston 24b. However, in the running part of the third piston 24c, a slight radial clearance is provided between the two pistons 24b, 24c, so that air can penetrate there.

The third piston 24c has a lower end fitted with a lip seal 40 conforming to the interior surface of the fixed body 22.

Each of the second and third pistons 24b, 24c has lugs 34 extending radially outwards and slidably mounted in vertical internal grooves 36 of the fixed body 22, as can be seen on the figure 4 . This makes it possible to block the rotation of the pistons relative to the fixed body 22 of the pipette.

The pistons participate with their lower ends in the delimitation of a single suction chamber 42, the lower part of which communicates with a channel 44 through which the cone holder 16 passes.

As an indicative example, the pipette is intended to allow the withdrawal of liquid in a range of volumes ranging from 0.5 to 1250 μl, or in a range of volumes ranging from 500 to 10000 μl. In the first case, there is for example provided a first piston 24a whose intrinsic sampling capacity is of the order of 50 μl, and a second piston 24b which, when associated with the first piston 24a, together have a capacity intrinsic sampling of the order of 350 μl, and finally a third piston 24c which, when associated with the first and second pistons 24a, 24b, has an intrinsic sampling capacity is of the order of 1250 μl.

• du premier piston 24a uniquement ;
• des premier et second pistons 24a, 24b ;
• des premier, second et troisième pistons 24a-24c.

Depending on the desired volume, adjusted by the operator via the dedicated control member on the pipette, the control control unit 10 is capable of ordering the start-up either:

• the first piston 24a only;
• first and second pistons 24a, 24b;
• first, second and third pistons 24a-24c.

To do this, the pipette 1 is equipped with a coupling module 50 specific to the invention, making it possible to couple and uncoupling each of the pistons with the control rod 12. More specifically, the module 50 is configured so to be able to be brought into three distinct configurations in which it ensures the coupling of the control rod 12 with respectively the first piston 24a only, the first and second pistons 24a, 24b, and finally the first, second and third pistons 24a-24c .

More specifically with reference to figures 3 and 4 , the coupling module 50 will be described in detail.

First of all, the module 50 includes an extension of the control rod 52 integral in translation with the control rod 12, and extending downward from this same rod. Preferably, the extension 52 is mounted screwed at its upper end to the lower end of the control rod 12.

The lower end of the extension 52, centered on the axis 9, permanently and permanently carries the first piston 24a, a screwed, glued or other connection, for example being provided between their respective ends.

In addition, the module 50 comprises a rotary coupling member 56, arranged around the control rod extension 52. Preferably, this member 56 is produced by means of two sliding parts, one with respect to the other, along the axis 9. It is first of all a high part 56a fixed in translation relative to the rod 12 and its extension 52, but movable in rotation relative to these, according to the axis 9. It is then a low part 56b coupled in rotation to the high part 56a, for example by means of a key 60.

A deployment spring 62 is arranged between the two parts 56a, 56b, so as to generate a force tending to separate them from one another. This deployment spring 62 is in abutment against an interior bearing surface of the lower part 56b, and a coupling ring of the upper ends of the upper part 56a and of the extension 52.

The lower part 56b is thus mounted movable in translation along the axis 9, relative to the extension 52 and to the control rod 12. It is also equipped, at its lower end, of at least one piston hooking finger 64, preferably two diametrically opposite fingers as shown on the figure 3 .

Each latching finger 64 extends radially outward from the bottom part 56b. As will be described below, the angular position of these fingers 64 conditions the number of pistons coupled to the module 50.

To vary the angular position of the fingers 64, the coupling module 50 further comprises a movement transforming body 66, intended to transform a translational movement into a rotational movement along the same axis 9. In fact, this body 66 cooperates with the upper part 56a of the rotary coupling member 56 so that a relative translational movement between them two along the axis 9, simultaneously leads to a relative rotation between them two along this same axis. It is therefore a question of obtaining a helical movement of the rotary coupling member 56, which is made possible by ramps provided on the body 66 as well as follower rollers carried by the rotary member 56.

More specifically, the member 56 is equipped with two follower rollers 68 arranged diametrically opposite, and mounted to rotate along the same transverse axis 76 orthogonal to the axis 9. With each follower roller 68, there is associated a first helical ramp 70a located inside the body 66, as well as a second helical ramp 70b also located inside the body 66, opposite the first ramp. The design is such that when each follower roller 68 cooperates with its first associated ramp 70a, it makes it possible to cause the rotation of the rotary member 56 according to a first direction of rotation 72a about the axis 9. Conversely, when 'it cooperates with its second associated ramp 70b, it makes it possible to cause the rotation of the rotary member 56 according to a second direction of rotation 72b opposite to the first direction.

It is also noted that each follower roller 68 is carried by a pin 74 for rotating support centered on the axis 76, this pin opening into a radial opening 78 of the movement transforming body 66.

The axial positioning of the rotary coupling member 56 relative to the body 66 is ensured by two compression springs, namely a first centering spring 80a tending to push the member 56 upward relative to the body 66, and a second centering spring 80b tending to push the rotary coupling member down relative to the movement transforming body 66.

To do this, the first spring 80a is housed inside the body 66 between a low end thereof and a shoulder 82 located at the high end of the rotary member 66, while the second spring 80b is housed inside the body 66 between an upper end of the latter and the same shoulder 82. It is also noted that it is on this shoulder that the follower rollers 68 are preferably mounted, via the pins 74.

Now referring to the figure 6 , in combination with figures 3 and 4 , the cooperation between the coupling module 50 and the first and second pistons 24b, 24c will now be described, it being understood that the first piston 24a remains permanently attached to this coupling module 50.

At its upper end 24b ', the second piston 24b has two diametrically opposite hooking slots 84b (only one being visible on the figure 6 ). Each slot 84b is oriented circumferentially, open in the same direction at one of its ends, and has a slot bottom at the opposite end. These slots 84b, intended to cooperate with the fingers 64 in the form of lugs, are thus defined by notches 86b comparable to those of a bayonet connection.

Similarly, at its upper end 24c ', the third piston 24c has two diametrically opposite hooking slots 84c (only one being visible on the figure 6 ). Each slot 84c is also oriented circumferentially, open in the same direction at one of its ends, and has a slot bottom at the opposite end. These slots 84c, also intended to cooperate with the fingers 64 in the form of lugs, are defined by notches 86c also comparable to those of a bayonet connection.

The slots 84b, 84c are grouped by couple. For the same pair of slots 84b, 84c such as that visible on the figure 6 , these are located facing each other radially. In other words, they are considered to be superimposed in the radial direction, only overlapping partially in the circumferential direction. Indeed, the two slots 84b, 84c of the same couple have different circumferential lengths, while having their split bottoms aligned in the radial direction. Consequently, in the preferred embodiment which is described and shown in the figures, this implies that each notch 86b provided on the second piston 24b and delimiting the slot 84b, is longer than the notch 86c provided on the third piston 24c and delimiting the slot 84c.

The width of the slots 84b, 84c is preferably identical, and provided so that the gripping fingers 64 can be moved circumferentially in and out of these slots. Preferably, the slit width is slightly greater than the diameter of the fingers.

With this configuration, the number of pistons coupled to the lower part 56b of the module 50 thus depends on the relative angular position between each finger 64 and its pair of associated slots 84b, 84c. The figure 6 shows this principle well, since in a first configuration of the module 50 shown with the finger 64 in solid lines, this same finger 64 adopts an angular position such that it is located outside the two slots 84b, 84c. In this first configuration, the two pistons 24b, 24c are not coupled, only the first piston remaining integral with the module 50. This first configuration is for example adopted by the control unit for pipetting volumes falling within a range ranging from 0.5 to 30 µl.

In a second configuration of the module 50, represented with the finger 64 in dotted lines in the middle of the figure 6 , each finger 64 adopts an angular position such that it is located in the slot 84b, but outside the slot 84c. The cooperation between finger 64 and notch 86b is similar to a bayonet connection. For example, an angular offset of 20 to 25 ° is provided between the position of the finger 64 of the first configuration, and that of the second configuration. In it, the two pistons 24a, 24b are thus coupled to the module 50, but not the third piston 24c. This second configuration is for example adopted by the control unit for pipetting volumes falling within a range from 30 to 300 μl.

In a third configuration of the module 50, represented with the finger 64 in dotted lines to the right of the figure 6 , the finger 64 adopts an angular position such that it is located in the slots 84b 84c, close to or in contact with the slot funds. The cooperation between finger 64 and notches 86b, 86c is akin to bayonet connections. For example, an angular offset of 20 to 25 ° is provided between the position of the finger 64 of the second configuration, and that of the third configuration. In the latter, the three pistons 24a-24c are thus coupled to the module 50. This second configuration is for example adopted by the control unit for pipetting volumes falling within a range from 300 to 1250 μl.

Now referring to Figures 7a to 7c , the operation of the pipette 1 will be described when its coupling module 50 is in the first configuration, namely with only its first internal piston 24a coupled to this module.

The figure 7a shows pipette 1 with its control rod in the high pipetting position, for example at the end of the suction stroke. The piston 24a coupled to the module 50 is thus in its highest position relative to the fixed body 22 of the pipette. As for the two other pistons 24b, 24c, they are in an inactive position as a bottom stop against the fixed body 22. At this stage, the follower rollers 68 are substantially centered relative to the movement transforming body 66, also in the high position.

The dispensing of the aspirated liquid is then controlled by the control button, which induces the actuation of the motor leading the control rod 12 to move downwards. During this dispensing stroke, the movement of the rod 12 downwards drives the module 50 which therefore also slides along the fixed body 22. The pistons 24b, 24c remain stationary, unlike the first piston 24a which descends. The status of the pipette at the end of the dispensation stroke is shown on the figure 7b , while the continuation of the descent of the rod 12 leads to the production of a purge stroke, the final state of which is shown in the figure 7c .

Now referring to Figures 8a to 8c , the operation of the pipette 1 will be described when its coupling module 50 is in the second configuration, namely with only its first and second pistons 24a, 24b coupled to this module.

The figure 8a shows pipette 1 with its control rod in the high pipetting position, for example at the end of the suction stroke. The pistons 24a, 24b coupled to the module 50 are in their highest position relative to the fixed body 22 of the pipette. During pipetting, the relative axial position of these two pistons remains unchanged. As for the third piston 24c, it remains in an inactive position as a bottom stop against the fixed body 22. At this stage, the follower rollers 68 are substantially centered relative to the movement transformation body 66, also in the high position.

The dispensing of the aspirated liquid is then controlled by the control button, which induces the actuation of the motor leading the control rod 12 to move downwards. During this dispensing stroke, the movement of the rod 12 downwards drives the module 50 which therefore also slides along the fixed body 22. The piston 24c remains stationary, unlike the pistons 24a, 24b which descend simultaneously. The status of the pipette at the end of the dispensation stroke is shown on the figure 8b , while the continuation of the descent of the rod 12 leads to the production of a purge stroke, the final state of which is shown in the figure 8c .

Now referring to Figures 9a to 9c , the operation of the pipette 1 will be described when its coupling module 50 is in the third configuration, namely with all of its pistons 24a-24c, coupled to this module.

The figure 9a shows pipette 1 with its control rod in the high pipetting position, for example at the end of the suction stroke. The pistons 24a-24c coupled to the module 50 are in their highest position relative to the fixed body 22 of the pipette. During pipetting, the axial relative position of these three pistons remains unchanged. At this stage, the follower rollers 68 are substantially centered relative to the movement transformation body 66, also in the high position. As in the other two configurations, the position of the rollers 68 within the module is not bound to change during pipetting.

The dispensing of the aspirated liquid is then controlled by the control button, which induces the actuation of the motor leading the control rod 12 to move downwards. During this dispensation stroke, the movement of the rod 12 towards the bottom drives the module 50 which therefore also slides along the fixed body 22. The three pistons 24a-24c then descend simultaneously, pushed by the rod 12 and the module 50. The state of the pipette at the end of the dispensing stroke is shown on the figure 9b , while the continuation of the descent of the rod 12 leads to the production of a purge stroke, the final state of which is shown in the figure 9c .

The figures 10a to 10c and the Figures 11a and 11b schematize an operation aiming to pass from the first configuration to the second configuration of the module 50. To do this, a first overtravel is ordered by the control unit, down from the purge end position such that shown on the figure 7c .

The body 66 first comes into low stop on the fixed body 22. As the first overtravel continues, the high part 56a of the rotary member 56 is rotated due to the support of the follower rollers 68 on their ramps 70a. This helical movement is transmitted to the lower part 56b, as well as to its attachment fingers 64. It takes place against the return force generated by the first centering spring 80a, by compressing the latter. During this movement, the fingers 64 of the lower part 56b then come into axial lower abutment against the upper ends 24b ', 24c' of the pistons 24b, 24c, this state corresponding to that shown on the figures 10a and 11a . Then, the first overtravel continues and the upper part 56a continues to be driven helically, while the lower part 56b only undergoes a rotation along the axis 9 in the first direction 72a, due to its blocking in translation. The relative translational movement between the two parts 56a, 56b takes place against the return force generated by the deployment spring 62, by compressing the latter.

During this rotation, the angular extent of which is perfectly controlled because it depends directly on the extent of the axial overtravel of the control rod 12, the latching fingers 64 penetrate into the slots 84b. However, this angular displacement of the fingers 64, for example of the order of 22.5 °, is not sufficient for them to enter the slot 84c. Insertion of fingers 64 into slots 84b cause the second piston 24b to couple with the module 50. This mechanical coupling state is shown in the figures 10b and 11b .

Once the coupling has been completed, the pipette control unit orders the rod 12 to be raised to the end of purge position, which has the consequence of simultaneously raising the first and second pistons 24a, 24b, like this. is shown on the figure 10c . The third piston 24c remains in its fixed position.

Then, pipetting operations can be ordered in a conventional manner, for volumes corresponding to the range associated with the assembly of the two pistons 24a, 24b.

The figures 12 to 12c and the Figures 13a and 13b schematize an operation aiming to pass from the second configuration to the third configuration of the module 50. To do this, another first overtravel of greater amplitude than the previous one is ordered by the control unit, downwards from the position purge limit switch as shown on the figure 12 .

The body 66 first comes into low stop on the fixed body 22. As the first overtravel continues, the high part 56a of the rotary member 56 is rotated due to the support of the follower rollers 68 on their ramps 70a. This helical movement is transmitted to the lower part 56b, as well as to its hooking fingers 64. During this movement, the fingers 64 of the lower part 56b then come into axial lower abutment against the upper end 24c 'of the piston 24c, this state corresponding to that shown on the figures 12a and 13a .

Then, the first overtravel continues and the upper part 56a continues to be driven helically downwards, while the lower part 56b only undergoes a rotation along the axis 9 in the first direction 72a, due to its blocking in translation. During this rotation, the angular extent of which is perfectly controlled because it depends directly on the extent of the axial overtravel of the control rod 12, the latching fingers 64 penetrate into the slot 84c. This angular displacement of the fingers 64 is for example of the order of 22.5 °, and sufficient to come against or near the bottom of the slots 84b, 84c. Insertion of fingers 64 in the slots 84c causes the third piston 24b to couple with the module 50. This state of mechanical coupling is shown in the figures 12b and 13b .

Once the coupling has been completed, the pipette control unit orders the rod 12 to be raised to the end of purge position, which has the consequence of raising the three pistons 24a-24c simultaneously, as shown on the figure 12c . Then, pipetting operations can be ordered in a conventional manner, for volumes corresponding to the range associated with the set of three pistons 24a-24c.

Of course, it is noted that a direct transition from the first to the third configuration can be ordered by the pipette control unit, by adapting the amplitude of the first stroke down accordingly.

The figures 14a to 14d and the Figures 15a and 15b schematize an operation aiming to pass from the third configuration to the second configuration of the module 50. To do this, a second overtravel is ordered by the control unit, upwards from a high pipetting position as shown on the figure 14a .

In this state of nominal volume sampling associated with the third configuration, the body 66 is in high abutment on the fixed body 22. As the second overtravel continues upwards, the high part 56a of the member 56 is rotated due to the support of the follower rollers 68 on their ramps 70b, as shown on the figure 15a . This helical movement is transmitted to the lower part 56b, as well as to its hooking fingers 64. It takes place against the return force generated by the second centering spring 80b, by compressing the latter. During this movement during which the two pistons 24b, 24c slide while remaining fixed in rotation, the fingers 64 in helical movement gradually escape from the slot 84c. At the end of the second overtravel, the fingers 64 are fully extended from the slots 84c, so that the third piston 24c is uncoupled from the module 50. This state is shown on the figures 14b and 15b .

Then, the pipette control unit orders a downward movement of the control rod 12, so that the fingers 64 push the third piston 24c into its low position, abutting against the fixed body 22. This phase is represented on the figure 14c . It precedes the final ascent phase of the module 50 and the two pistons 24a, 24b, thanks to an axial displacement upwards of the control rod 12 as shown diagrammatically on the figure 14d .

Then, pipetting operations can be ordered in a conventional manner, for volumes corresponding to the range associated with the assembly of the two pistons 24a, 24b.

The Figures 16a and 16b as well as Figures 17a and 17b schematize an operation aiming to pass from the second configuration to the first configuration of the module 50. To do this, another second overtravel of greater amplitude than the previous one is ordered by the control unit, upwards from a high pipetting position as shown on the figure 16a .

In this state of nominal volume withdrawal associated with the second configuration, the body 66 is in high stop on the fixed body 22. As the second overtravel continues upwards, the high part 56a of the member 56 is rotated due to the support of the follower rollers 68 on their ramps 70b, as shown on the figure 17a . This helical movement is transmitted to the lower part 56b, as well as to its hooking fingers 64. During this movement during which the piston 24b slides while remaining fixed in rotation, the fingers 64 in helical movement gradually escape. slots 84b. At the end of the second overtravel, the fingers 64 are fully extended from the slots 84b, so that the second piston 24b is uncoupled from the module 50. This state is shown on the figures 16b and 17b .

Then, the pipette control unit orders a downward movement of the control rod 12, so that the fingers 64 push the second piston 24b into its low position, abutting against the fixed body 22 or against the third piston 24c already in the bottom stop position. This phase, similar to that shown on the figure 14c , precedes the final ascent phase of the module 50 and the single piston 24a, by virtue of an axial displacement upwards of the control rod 12.

Then, pipetting operations can be ordered in a conventional manner, for volumes corresponding to the range associated with the single first piston 24a.

Here also, it is noted that a direct passage from the third to the first configuration can be ordered by the pipette control unit, by adapting the amplitude of the second stroke upwards accordingly.

Of course, various modifications can be made by those skilled in the art to the invention which has just been described, only by way of nonlimiting examples.

Claims (15)

1. A sampling pipette (1) comprising:

   - a pipette fixed body (22);

   - a control rod (12) translationally movable relative to the pipette body (22), along a longitudinal axis (9) of the pipette; and

   - a suction chamber (42);

   characterised in that it also includes:

   - a set of N concentric pistons (24a-24c), N corresponding to an integer higher than or equal to two, each of the pistons participating in delimiting said suction chamber (42); and

   - a module (50) for coupling the control rod (12) with the set of N concentric pistons (24a-24c), said module being configured so as to be capable of being brought into N distinct configurations in which it provides coupling of the control rod (12) with 1, 2, ..., N pistons respectively.
2. The sampling pipette according to claim 1, characterised
   in that the coupling module (50) comprises at least one piston attachment finger (64) radially extending relative to the longitudinal axis (9) of the pipette,
   in that at least N-1 pistons (24b, 24c) each have an attachment slot (84b, 84c) circumferentially oriented and open, the slots having different circumferentially lengths for each of said at least N-1 pistons,
   and in that said pipette is configured such that the attachment finger (64) is capable of being circumferentially moved in and out of the slots (84b, 84c) radially facing each other.
3. The sampling pipette according to claim 2, characterised in that the coupling module (50) comprises a coupling rotary member (56) provided at its bottom end with said finger (64), and rotatably mounted at its top end to the control rod (12), along the longitudinal axis (9) of the pipette.
4. The sampling pipette according to claim 2, characterised in that the coupling rotary member (56) is made using two parts (56a, 56b) slidably mounted with respect to each other, along the longitudinal axis (9) of the pipette, an expansion spring (62) being arranged between both these parts (56a, 56b) so as to generate a strain tending to move them away from one another.
5. The sampling pipette according to claim 4, characterised in that the coupling module (50) includes a control rod extension (52) translationally integral with the control rod (12), and in that said two parts of the coupling rotary member are formed by a top part (56a) and a bottom part (56b) respectively, the latter being translationally movably mounted along the longitudinal axis (9), relative to the control rod extension (52).
6. The sampling pipette according to any of claims 3 to 5, characterised in that the coupling module (50) further comprises a motion transforming body (66) cooperating with the coupling rotary member (56) such that a relative translation movement between them along the longitudinal axis (9) simultaneously results in a relative rotation with respect to each other, also along the longitudinal axis (9).
7. The sampling pipette according to claim 6, characterised in that the motion transforming body (66) includes at least one first helical ramp (70a) as well as at least one second helical ramp (70b), and in that the coupling rotary member (56) is provided with a follower roller (68) which, when it cooperates with the first ramp (70a) enables the rotation of the coupling rotary member (56) to be caused along a first direction of rotation (72a) and which, when it cooperates with the second ramp (70b) enables the rotation of the coupling rotary member (56) to be caused along a second direction of rotation (72b).
8. The sampling pipette according to claim 7, characterised in that it is designed such that the rotation of the coupling rotary member (56) along the first direction of rotation (72a) is achieved by a first overstroke downwards of the control rod (12) from a purge stroke end position thereof, and in that the rotation of the coupling rotary member (56) along the second direction of rotation (72b) is achieved by a second overstroke upwards of the control rod (12) from a top pipetting position of this control rod.
9. The sampling pipette according to claim 8, characterised in that the first overstroke is made acting against a strain generated by a first centring spring (80a) tending to repel the coupling rotary member (56) upwardly relative to the motion transforming body (66), and in that the second overstroke is made acting against a strain generated by a second centring spring (80b) tending to repel the coupling rotary member (56) downwardly relative to the motion transforming body (66).
10. The sampling pipette according to any of the preceding claims, characterised in that it is a pipette configured such that the movement of the control rod (12) is made manually or in a motorised manner.
11. The sampling pipette according to any of the preceding claims, characterised in that the number N of pistons (24a-24c) is higher than or equal to three.
12. The sampling pipette according to any of the preceding claims, characterised in that it is designed so as to be able to sample a volume range from 0.5 to 1,250µl, or designed so as to be able to sample a volume range from 500 to 10,000µl.
13. The sampling pipette according to any of the preceding claims, characterised in that it comprises a control member for adjusting the volume to be sampled (8).
14. The sampling pipette according to any of the preceding claims, characterised in that the innermost piston (24a) is permanently integral with the coupling module (50).
15. The sampling pipette according to any of the preceding claims, characterised in that it is a single-channel or multi-channel pipette.

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