Improved multi-channel pipetting system

Abstract

The invention relates to a device for a multichannel pipetting system, comprising a piston carrier (34), a guide rod (38) of the piston carrier, which is slidably mounted in a guide member (40), a plurality of pistons (20a, 20b) having a lower end slidably accommodated in a suction chamber, and a piston head (56) mounted on the piston carrier by means of a mechanical connection (62). According to the invention, the mechanical connection (62) comprises two contact points (64a, 64b) which together define a piston head rotation axis (66) which is oriented orthogonally with respect to a transverse direction (10) of the pipetting system and a longitudinal central axis (14), and the device additionally comprises a resilient return means (68) associated with the pistons (20a, 20b) which forces the piston head (56) upward against the piston carrier (34) in order to establish the two contact points (64a, 64b).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of multi-channel pipetting systems, such as multi-channel sampling pipettes, also known as laboratory pipettes or vented liquid transfer pipettes, intended for calibrated sampling and introduction of liquids in a container.

[0002] The present invention is preferably applicable to sampling pipettes intended to be held in the hand by an operator during the operations of sampling and dispensing liquids, but also to automatic pipetting systems. BACKGROUND

[0003] Multi-channel sampling pipettes are known from the prior art, which have a design of the type integrating a body forming a handle and a lower part having at its end several pipette sampling cone holder tips, the known function of which is to carry sampling cones, also known as consumables.

[0004] In a known manner, the basic principle of a multi-channel pipette is based on the variation of the volume, which leads to a drop in pressure and the rise of the liquid in the sampling cone. Gravimetric specifications are generally established according to the difference in volume delivered between each pipetting and between each channel of the multi-channel pipette. This leads to the need to control the movement of all the pistons that generate a change in pressure.

[0005] On a manual, also called mechanical, motorized or hybrid multi-channel pipette, a piston holder extending in the transverse direction of the pipette is provided, which is generally called a "rake". A rod for guiding the piston holder is also provided, which extends parallel to the central longitudinal axis of this same pipette. In addition, the guiding member allows the guiding rod to be slidably guided along the central longitudinal axis. In this case, a plurality of pistons are distributed along the piston holder, each having a lower end slidably housed in a suction chamber, and a piston head mounted on the piston holder via a mechanical connection for mounting the piston on the piston holder.

[0006] Each mechanical connection for mounting the piston on the piston holder generally comprises a flat support orthogonal to the plane of the piston, thus giving this connection a certain rigidity. This can therefore generate a net torque, with an axis perpendicular to the plane of the piston and passing through the axis of the sliding connection of the guiding rod. This parasitic torque leads to two main disadvantages, the first of which consists in observing a "rake effect", and the second of which corresponds to the non-negligible friction of the piston holder and the other moving elements of the pipette during their translational movement.

[0007] As a reminder of the first drawback, the rake effect is quantified by the volume difference transported between the two opposite extreme channels of a multichannel pipette. This effect is therefore directly affected by the angular amplitude of the displacement of the piston carrier in the play of the sliding guide connection of the rod supporting this same piston carrier. The weight analysis performance of the multichannel pipette is therefore limited due to the rake effect observed on the current design.

[0008] As regards the second drawback related to the friction and possible jamming of the moving elements of the multichannel pipette, the latter is affected in terms of ergonomics, in particular in terms of pipetting and purging force.

[0009] It should be noted that the same or similar drawbacks are observed on motorized or hybrid pipettes, or on any other type of multichannel pipetting system. Alternatively, it can be a box forming the lower part of an articulated arm intended to be connected to an automatic device.

[0010] Furthermore, on a multichannel pipette comprising a return and / or purging spring, this spring generates another parasitic torque on the guide rod when the spring is compressed, the axis of which corresponds to the translation axis of the guide rod within the connection sliding guide. The parasitic torque is transmitted to the piston carrier, as a result of which the piston carrier is subjected to another parasitic rotational movement around the aforementioned translation axis. This is another source of pipetting stroke difference between the pistons depending on their distance from the central longitudinal axis of the pipette. This also creates a risk of additional friction / jamming between the piston carrier and the fixed surrounding elements of the pipette.

[0011] In summary, the return and / or purging spring can further reduce the weight analysis performance of the pipette and the ergonomics of the use of the pipette in terms of pipetting and purging force. SUMMARY

[0012] The aim of the present invention is therefore to propose a solution that at least partially overcomes the above-mentioned problems encountered in the solutions of the prior art.

[0013] For this purpose, the invention first relates to a device for a multichannel pipetting system, the device comprising:

[0014] - a piston carrier extending in a transverse direction of the pipetting system;

[0015] - a rod for guiding the piston carrier, the guide rod extending parallel to a central longitudinal axis of the pipetting system and orthogonally to the piston carrier;

[0016] - means for guiding the guide rod along the central longitudinal axis, the guide rod being slidably mounted in the guide means;

[0017] - a plurality of pistons distributed along the piston carrier, each piston having a lower end slidably housed in a suction chamber, and a piston head mounted on the piston carrier via a connection mechanism for mounting the piston on the piston carrier;

[0018] - a row of sampling cone carrier ends distributed along the transverse direction of the pipetting system, each end being in communication with a respective one of the suction chambers.

[0019] According to the invention, for at least one of the pistons and preferably for several or all of the pistons, the mechanical mounting connection comprises two contact points which together define an axis of rotation of the piston head, which is oriented orthogonally or substantially orthogonally to the transverse direction and to the central longitudinal axis of the pipetting system. The device further comprises elastic return means associated with said piston, which force the piston head against the piston carrier for establishing the two contact points.

[0020] The invention thus breaks with the principle generally implemented on multi-channel pipetting systems, namely the fact of providing the connections between the piston carrier and the pistons with a relatively high rigidity, resulting in the embedding of the heads of the pistons in the piston carrier. In contrast, in the invention, a certain flexibility is introduced into these connections, so that the piston head can pivot about its axis of rotation, which is defined by the two contact points with the piston carrier.

[0021] This degree of freedom of movement admitted at the piston head first allows to limit the rake effect on the piston carrier, which advantageously results in a gain in terms of precision / repeatability, thus allowing the pipetting system to obtain better gravimetric performance. This degree of freedom of movement also allows to limit the risk of friction and jamming of the elements in translation, in particular the piston carrier and the pistons. This advantageously results in a reduction of the pipetting and purging forces, thus leading to better ergonomics of the pipettor when it is manual, or to a reduction in the size of the drive motor and battery on motorized and hybrid pipettors.

[0022] Moreover, thanks to the specific positioning of the two contact points of the mechanical mounting connection of the piston head, it becomes easy to use the seals equipping the pistons to absorb the parasitic torques generated by the return and / or purging springs. Indeed, such parasitic torques applied along the translation axis of the guide rod are directly transmitted to the piston carrier, then to the piston, and finally to the seals, which establish a radial contact point in their respective suction chamber. This way of absorbing the parasitic torques along the translation axis of the guide rod via the piston seals greatly limits the rake effect, while reducing the friction of the moving parts of the pipettor. The gravimetric performance of the pipettor is further improved, and the pipetting and purging forces can be further reduced.

[0023] Moreover, the use of the piston seal to absorb such parasitic torques allows to simplify the design of the pipetting system and, consequently, to reduce its weight, since the opposite end of the piston carrier is no longer required to be guided by a fixed part of the system. On the contrary, the opposite end of the piston carrier can remain free, without being connected with other parts of the pipetting system.

[0024] Finally, it should be noted that the proposed solution advantageously allows the piston seal to withstand a high number of cycles in high-pressure sterilization, while continuing to provide the required sealing at their associated suction chambers and without generating friction forces that are detrimental to ergonomics. The proposed solution thus proves to be particularly effective in terms of weight analysis and ergonomics of use, while ensuring a satisfactory life of the piston seal.

[0025] The present invention also preferably comprises at least one of the following optional features, considered individually or in combination.

[0026] Preferably, the elastic return means are formed by a helical spring of substantially conical shape, the cross section of which tapers upwards from the bottom. The shape and orientation of this spring facilitate the pivoting of the piston head around the axis of rotation of the piston head, while ensuring that the piston is axially pressed against the piston carrier.

[0027] Alternatively, the elastic return means are formed by a spring in the form of a deformed wire.

[0028] The piston carrier has two opposite free transverse ends.

[0029] The guide rod is slidably mounted in the guide member via two sliding pivot connections spaced apart from each other along the central longitudinal axis.

[0030] Each piston carries, at its lower end, a seal which bears on the inner surface of the suction chamber associated with the piston.

[0031] Preferably, the seal is a lip seal.

[0032] The two contact points of each mechanical mounting connection are arranged symmetrically with respect to the axis of the associated piston.

[0033] The two contact points of each mechanical mounting connection are implemented in either of the following ways:

[0034] - using an annular surface provided on the piston and two flat surfaces provided on the piston carrier, inclined with respect to each other;

[0035] - using a spherical surface provided on the piston and two flat surfaces provided on the piston carrier, inclined with respect to each other;

[0036] - using a flat surface provided on the piston and two spherical surfaces provided on the piston holder;

[0037] - using a flat surface provided on the piston and two spherical surfaces provided on the piston holder;

[0038] - using a spherical surface provided on the piston and two spherical surfaces provided on the piston holder;

[0039] - using a spherical surface provided on the piston and two cylindrical surfaces with an evolute axis provided on the piston holder; or

[0040] - using an annular surface provided on the piston and two cylindrical surfaces with an evolute axis provided on the piston holder.

[0041] According to a preferred embodiment of the application, the suction chambers have parallel chamber axes.

[0042] All chamber axes can be arranged in one and the same transversal plane of the pipetting system, or in two separate parallel transversal planes of the pipetting system in a staggered manner. In the latter case, the piston heads can also be arranged in the same two transversal planes defined by the chamber axes in a staggered manner, so that these chamber axes coincide pairwise with the piston axes. Alternatively, the piston heads can all be aligned along a transversal line arranged parallel to and between the two transversal planes defined by the chamber axes, so that the piston axes are inclined with respect to their corresponding chamber axes.

[0043] Preferably, the piston holder is made in two parts fixed to each other, and between which the piston heads and the elastic return means are arranged. Alternatively, the piston holder is made in one piece, for example for pipettors intended for sampling small volumes, such as 200 μΙ_ or 300 μΙ_.

[0044] Finally, the application also relates to a multichannel pipetting system comprising such a device, which pipetting system is preferably a manual, motorized or hybrid sampling pipettor. Alternatively, the multichannel pipetting system can be for example an automated pipetting system.

[0045] Other advantages and features of the application will appear in the following non-limiting detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0046] This description will be made with respect to the appended drawings, in which:

[0047] [ Figure 1 ] shows a front view of a vented multichannel sampling pipettor;

[0048] [ Figure 2a view of the device according to the first preferred embodiment of the application, which forms an integral part of the pipette shown in the previous figure;

[0049] [ Figure 2a ] is a perspective view of the lower part of the device shown in Figure 1 and Figure 2 is a perspective view of the upper part of the device shown in

[0050] [ Figure 3 ] is a perspective view of the lower part of the device shown in Figure 2 and Figure 2a is an axial sectional view of the upper part of the device shown in

[0051] [ Figure 4 ] is a perspective view of the lower part of the device shown in Figure 2 and Figure 2a is a perspective view of the lower part of the device shown in

[0052] [ Figure 5 ] is a side view of the lower part of the device shown in

[0053] [ Figure 5a ] is a perspective view of the piston holder implemented in the first preferred embodiment;

[0054] [ Figure 5b ] is an enlarged perspective view of a part of the piston holder shown in the previous figure;

[0055] [ Figure 6 ] is an enlarged front view of the part of the device shown in the previous figure, showing the mechanical connection for mounting the piston on the piston holder;

[0056] [ Figure 7a ] is a perspective view of a part of the mechanical mounting connection shown in the previous figure;

[0057] [ Figure 7b ] is a perspective view of a part of the mechanical mounting connection according to an alternative;

[0058] [ Figure 7c ] is a perspective view of a part of the mechanical mounting connection according to yet another alternative;

[0059] [ Figure 7d ] is a perspective view of a part of the mechanical mounting connection according to yet another alternative;

[0060] [ Figure 7e ] is a perspective view of a part of the mechanical mounting connection according to yet another alternative;

[0061] [ Figure 7f ] is a perspective view of a part of the mechanical mounting connection according to yet another alternative;

[0062] [ Figure 7gis a partial perspective view of a mechanical mounting connection according to a further alternative;

[0063] [ Figure 8 ] shows Figure 5 a perspective view of a part of the device shown;

[0064] [ Figure 9 ] shows a view similar to Figure 6 the view of

[0065] [ Figure 10 ] shows a view similar to Figure 5 the view of

[0066] [ Figure 11 ] shows a perspective view of a piston holder implemented in the second preferred embodiment;

[0067] [ Figure 12 ] shows a partially exploded perspective view showing a device according to a third preferred embodiment of the invention;

[0068] [ Figure 13 ] is a cross-sectional view along a plane of the piston holder normal to the plane of the previous figure; and

[0069] [ Figure 14 ] is a cross-sectional view along a plane of the piston holder parallel to Figure 12 the plane of DETAILED DESCRIPTION

[0070] Reference is first made to Figures 1 to 3 , showing a multi-channel sampling pipettor 1 according to a preferred embodiment of the invention. However, the invention is not limited to pipettors, but is applicable to any multi-channel pipetting system, in particular to automated pipetting systems, known as automated devices.

[0071] In this embodiment of Figures 1 to 3 , the pipettor is preferably intended for sampling of large volumes, for example 1200 μΐ. However, its design is also applicable to sampling of smaller volumes, for example 200 μΐ or 300 μΐ.

[0072] The manually, motorized or hybrid vented pipettor 1 comprises in an upper portion a body forming a handle 2, and comprises a lower portion 4 integrating at its lower end sampling cone holder tips 6 onto which cones or consumables 8 are intended to be press-fitted.

[0073] The sampling cone holder ends 6 are spaced apart from each other in the lateral direction of the pipette system, also known as the lateral direction of the pipette, and indicated by arrow 10. Each end 6 has a through-hole 12 that communicates with the aspiration chambers 13a, 13b at its upper end and with the sampling cone 8 at its lower end. The through-hole 12 may or may not be centered on its associated end 6, that is, it may or may not be centered on the central axis 7 of the end of the press-fitted cone.

[0074] The pipette 1 has a central longitudinal axis 14, which also corresponds to the central longitudinal axis of the lower part 4 and the central longitudinal axis of the device 32 specific to this invention. This axis 14, parallel to the height direction 15 of the pipette, is orthogonal to the transverse direction 10. The central longitudinal axis 14 passing through the handle 2 is generally positioned such that the same number of ends 6 are provided on both sides of the handle in the transverse direction 10. Furthermore, the axis 14 is generally parallel to the axis of the through hole 12 and the axis 7 of their associated ends 6 and the cone 8, and also parallel to the height direction 15, which corresponds to the sliding / translational direction of the movable elements of the pipette, as will be described below.

[0075] exist Figures 1 to 3 In the example shown, twelve ends 6 are arranged aligned in direction 10 to form a single row of ends laterally. Furthermore, the central axis 7 of each end 6 intersects the same straight line 9 extending in direction 10.

[0076] As those skilled in the art will know, the lower part 4 is preferably threaded onto the body 2 that forms the handle.

[0077] One of the special features of this invention lies in the design of the device 32, which almost entirely forms the lower part 4 and a small portion of the handle 2. The device 32... Figure 2 The full text is shown, but the description of its first preferred embodiment will pertain to all. Figures 2 to 9 conduct.

[0078] In a known manner, the lower part 4 includes a fixed body 16 and a component 19 that can move relative to the fixed body 16 in a sliding direction 15.

[0079] The lower fixing body 16 of the pipette is made of several components that are integrally formed, attached, or manufactured as a single piece. These are particularly the aspiration chambers 13a and 13b and the cone support end 6, which are completed by a fixing transverse retaining plate 21 extending across the upper ends of the chambers 13a and 13b. Figure 2aPartially shown, an outer removable cover 17 is arranged around the fixed body 16, which cover generally covers the lower part of the device 32, so that only the lower part of the tips 6 protrude outside this cover 17. The cover has recesses inside, which are used to accommodate the edges of the fixed transverse retaining plate 21.

[0080] The movable assembly 19 in turn comprises inside the cover 17 a piston carrier 34, also called rake, which is roughly in the shape of a strip extending in the transverse direction 10. The pistons 20a, 20b are distributed along the piston carrier, regularly spaced apart from each other in the transverse direction 10, and are each oriented parallel to the axis 14. The piston carrier 34 is located as a whole above the pistons 20a, 20b, so as to be able to accommodate the piston heads. More precisely, these piston heads are prevented from translating in both directions of the sliding direction 15 by the piston carrier 34, so as to be able to follow the back-and-forth movement of the piston carrier in the same direction.

[0081] Each piston 20a, 20b has a lower end which is slidably accommodated in one of the associated suction chambers 13a, 13b, which are each in communication with one of the tips 6.

[0082] The movable assembly 19 of the pipette lower part 4 is fixedly connected to a guide rod 38 of the piston carrier 34. The guide rod 38 extends parallel to the central longitudinal axis 14, for example the guide rod is centered on the central longitudinal axis, which means that this rod 38 also extends orthogonally to the piston carrier 34. The guide rod passes through the handle 2, is slidably mounted in a fixed guide member 40 along the axis 14, which fixed guide member forms an integral part of the lower part of the pipette 4, while also penetrating into the handle 2.

[0083] More particularly, reference is made to Figure 3 , showing the guide rod 38 slidably accommodated in the fixed guide member 40 along the axis 14. Radially between the two, a return spring 42 and a purging spring 44 are provided, the latter for pipetting operations. These springs are cylindrical helical compression springs, axially supported on the guide rod 38. In the upper part of this rod 38, a shoulder 46a cooperates with the inner surface of the hollow guide member 40, so as to form a first sliding pivot connection. Furthermore, at its lower end, the guide member 40 has a hole 46b through which the rod 38 passes with a minimum clearance, so as to form a second sliding pivot connection spaced apart from the first sliding pivot connection in the direction 15. The spacing between the two connections is therefore as large as possible, so as to obtain an effective guide and to best limit the parasitic play of the guide rod 38.

[0084] For this first preferred embodiment, Figures 3 to 5One of the particularities of the arrangement of the pipette with respect to the chambers 13a, 13b and the pistons 20a, 20b is shown. The pistons are arranged in a staggered manner so as to form two transversal and parallel rows. The first pistons 20a form a first row of pistons by fitting in a first transversal plane PI of the pipette, that is to say, the piston axes 48a of these first pistons 20a are all fitted in the same transversal plane PI parallel to the directions 10 and 15. Similarly, the second pistons 20b form a second row of pistons by inscribing in a second transversal plane P2 of the pipette, which is parallel to and different from the plane PI. Thus, the piston axes 48b of these second pistons 20b are all inscribed in the same second transversal plane P2, also parallel to the directions 10 and 15. Moreover, in this first embodiment, the piston axes 48a, 48b are parallel to each other and the two planes PI, P2 are located on either side of the axis 14.

[0085] This particular arrangement of the pistons also applies to the suction chambers 13a, 13b. Indeed, the chambers are arranged in a staggered manner so as to form two transversal and parallel rows. The first chambers 13a form a first row of chambers by fitting in the first transversal plane PI, that is to say, the chamber axes 50a of these first chambers 13a are all fitted in the same transversal plane PI, coinciding in pairs with the piston axes 48a of the first associated pistons 20a. Similarly, the second chambers 13b form a second row of chambers by fitting in the second transversal plane P2, that is to say, the chamber axes 50b of these second chambers 13b are all fitted in the same second transversal plane P2, merging in pairs with the piston axes 48b of the associated second pistons 20b.

[0086] As shown in Figure 5a , Figure 5b and Figure 6 , in order to implement this particular arrangement, the piston holder 34 comprises a first series of seats 52a aligned in the transversal plane PI and a second series of seats 52b aligned in the plane P2. The seats 52a are arranged to accommodate the piston heads 56 of the first pistons 20a, while the seats 52b are arranged to accommodate the piston heads 56 of the first pistons 20b.

[0087] Figure 5 It is shown that the lower end of each piston 20a, 20b is provided with a seal 47 which bears on the inner surface 49 of the associated suction chamber 13a, 13b. The seal 47, which is preferably a lip seal made of elastomeric material, but other shapes are also contemplated without departing from the scope of the invention, supports the piston head 56 in the piston holder 34.

[0088] The manner in which the piston head 56 cooperates with the piston holder is particular to the invention and will be described with reference to Figure 6 . In this regard, it is noted that this Figure 6The teachings of the first piston 20a apply to the second piston 20b as well. In the following, for the sake of convenience, only the first piston 20a will be mentioned.

[0089] First, the piston holder 34 is made in two parts 34a, 34b, which are fixed one on top of the other by stacking in the direction 15. The main part 34a is located above the other part, and it is this main part which has a lower face which is configured to reveal seats 52a, 52b which open downward for receiving the piston head 56. The other part 34b forms a simple closed lid, pierced with passage holes 58 for the pistons 20a, 20b. Thus, the passage holes 58 are aligned in pairs with the seats 52a, 52b so as to form a space 60 in which the piston head 56 is arranged. Alternatively, it is still possible to manufacture the piston holder 34 in a single piece, that is to say, for example, integrally / monolithically by molding. Moreover, such a solution of manufacturing the holder 34 in one piece is preferred, for example, for pipette lower parts intended for sampling small volumes, such as 200 μΙ_ or 300 μΙ_.

[0090] Figure 6 A mechanical connection 62 for mounting the piston head 56 on the piston holder 34 is shown. This connection 62 is preferably used for all the pistons 20a, 20b of the pipette. It comprises two contact points 64a, 64b which together define the rotation axis 66 of the piston head. These two points of connection 62 make the rotation axis 66 of the piston head oriented orthogonally or substantially orthogonally to the transverse direction 10 and to the axis 14. In other words, this rotation axis 66 is oriented orthogonally to the strip-shaped piston holder 34, which allows the piston 20a to pivot around its head relative to the piston holder 34 in a transverse plane defined by these two same elements 20a, 34.

[0091] The two contact points 64a, 64b are arranged symmetrically about the piston axis 48a, and moreover, diametrically opposite on the seat 52a.

[0092] To maintain the two contact points 64a, 64b, the device 32 also comprises a return spring 68 which forces the piston head 56 upward against the seat 52a of the piston holder 34. Here, the spring 68 is a generally conical-shaped coil spring whose cross section tapers upward from the bottom, and which is preferably centered on the piston axis 48a. The shape and orientation of this spring 68 facilitate the pivoting of the piston head 56 around the rotation axis 66, while ensuring that the piston 20a is axially pressed against the piston holder 34. The spring 68 housed in the space 60 thus has a lower end bearing on the closed lid 34b and an upper end of smaller diameter bearing on the shoulder 70 of the piston 20a.

[0093] Figures 7a to 7gSeveral geometric alternatives for obtaining the two contact points 64a, 64b of the mechanical mounting connection 62 are shown.

[0094] First, in Figure 7a , a surface 70 is provided on the piston head 56, centred on the piston axis 48a, which surface 70 is here annular. This surface is supported on two members 72 of the seat 52a, arranged symmetrically about the piston axis 48a, in two-point bearing. Here, the two members 72 are two flat surfaces inclined relative to each other and parallel to the transverse direction 10, which surfaces 72 are in Figure 5b , also visible.

[0095] In Figure 7b , the surface 70 is a spherical surface, and this surface contacts two inclined flat surfaces 72 provided on the piston carrier.

[0096] In Figure 7c , the surface 70 is a conical surface, and this surface contacts two spherical surfaces 72 provided on the piston carrier.

[0097] In Figure 7d , the surface 70 is a flat surface normal to the piston axis 48a, and this surface contacts two spherical surfaces 72 provided on the piston carrier.

[0098] In Figure 7e , the surface 70 is a spherical surface provided on the piston, and this surface contacts two spherical surfaces 72 provided on the piston carrier.

[0099] In Figure 7f , the surface 70 is a spherical surface, and this surface contacts two cylindrical surfaces 72 provided on the piston carrier, which cylindrical surfaces have axes that intersect at a point on the piston axis 48a.

[0100] Finally, in Figure 7g , the surface 70 is an annular surface with the axis 48a, and this surface contacts two cylindrical surfaces 72 provided on the piston carrier, which cylindrical surfaces still have axes that intersect at a point on the piston axis 48a.

[0101] With reference to Figure 8 and Figure 9 , various advantages conferred by the invention will be described.

[0102] First of all, thanks to the flexibility introduced into the mechanical mounting connection 62, the piston head 56 of each piston 20a, 20b can indeed pivot about its rotation axis 66 defined by the two contact points 64a, 64b. This degree of freedom of movement allows to limit the rake effect on the piston support 34, which advantageously leads to a gain in terms of precision / repeatability and to better gravimetric performance. This degree of freedom of movement also allows to limit the risk of friction and jamming of the elements in translational movement, in particular the piston support 34 and the pistons 20a, 20b. This advantageously leads to a reduction of the pipetting and purging forces, thus to a better ergonomics of use of the pipette.

[0103] Moreover, thanks to the particular positioning of the two contact points 64a, 64b, it is possible to easily absorb the parasitic torque generated by the return and / or purging spring, which is exerted along the axis 14 and in Figure 8 is schematically indicated by the arrow 74. This absorption takes place using the seals 47 equipping the lower end of the pistons 20a, 20b. In fact, this parasitic torque 74 is transmitted directly to the piston support 34, then to the pistons 20a, 20b and finally to the seals 47, which establish radial contact points 76 on the inner surface 49 of their respective chamber 13a, 13b. These radial contacts, one of which is schematically indicated by the arrow 78 in Figure 8 , are maintained without parasitic rotation of the pistons in a plane integrating the axis 66 and parallel to the direction 15, in particular thanks to the return force of the spring 68, schematically indicated by the arrow 80 in Figure 9 .

[0104] This way of absorbing the parasitic torque along the axis 14 via the piston seals 47 greatly limits the rake effect, while reducing the friction of the moving elements of the pipette. The gravimetric performance is improved and the pipetting and purging forces are reduced.

[0105] Moreover, the use of the piston seals 47 to absorb this parasitic torque along the axis 14 allows to simplify the design of the pipette and to reduce its weight. Indeed, the opposite lateral ends of the piston support 34 are no longer required to be individually guided by the fixed part of the pipette and, moreover, these lateral ends are preferably free in the internal space defined by the lower cover 17, as shown in Figure 2a . By "free" end is meant an end that is not directly mechanically connected to other parts of the pipette, in particular to the fixed part.

[0106] Finally, the proposed solution also allows the piston seals 47 to withstand a large number of autoclave cycles, while providing the required sealing at their associated chambers 13a, 13b. In this regard, it should be noted that, in the field of pipetting systems, autoclaving comprises an operation that allows the sterilization of parts in the presence of saturated steam, at certain temperature and pressure conditions. The combined action of temperature, pressure and water vapor can alter the dimensions of the parts, in particular the joints. However, thanks to the rotational freedom given to each piston, the present invention allows the seals to continue to ensure a good sealing in their chamber, even if there is limited contact, since the position of the seal is always kept optimal thanks to its ability to reposition in the chamber. Figure 10 and Figure 11 A second preferred embodiment of the invention is shown, in which the piston heads 56 are all aligned along a transversal line 84 arranged parallel to the transversal planes P1 and P2 defined by the axes 50a, 50b of the chambers 13a, 13b, thus remaining arranged in a staggered manner. The transversal line 84 is also located between the two planes P1 and P2. Thus, for the first pistons 20a, the piston axes 48a, 48b are all inclined in a given direction with respect to their corresponding chamber axes 50a, 50b, while for the second pistons 20b, they are inclined in the opposite direction. The inclination of the piston axes 48a, 48b varies during translation, but varies within a rather small angular range, for example from 5° to 10°. During pipetting, the elastic deformation of the springs 68 within the mechanical link 62 allows this variation in inclination.

[0107] In this second embodiment, the seats 52a, 52b for receiving the piston heads 56 can also all be aligned on the piston carrier 34 along the transversal line 84. This advantageously limits any secondary raking effect that can be generated by the offset between the two rows of seats 52a, 52b transversal to each other, for example in Figure 5a and Figure 5b as can be seen in.

[0108] Of course, the person skilled in the art can make various modifications to the invention just described, by way of non-limiting example only, the scope of which is limited by the attached claims. For example, the invention can also be applied in the case where the axes of all the chambers and the axes of all the pistons are located in the same plane, as shown for example in the third embodiment intended for sampling of smaller volumes, Figures 12 to 14 .

[0109] In this third embodiment, in which the features can be combined and / or interchangeable with those of the above-described embodiments, each tip 6 and its associated suction chamber 13a, 13b are made in one piece.

[0110] In these Figures 12 to 14In this third embodiment, only the upper part of the head of each piston 20a, 20b is shown. The lower part, not shown, is intended to be coupled with this upper part. According to a first possibility considered for example for volume samplings of the 200 μL and 300 μL type, the lower part of the piston is arranged to receive the extremity 100 of the upper part by adaptation. According to a second possibility considered for example for smaller volume samplings of the 10 μL or 20 μL type, the lower part of the piston is arranged to be coupled by press fitting into a hole 102 of the upper part of the piston head 56.

[0111] In this third embodiment, another particularity lies in the elastic return means for holding the piston heads 56 against the rake 34. Here, these means take the form of clips 104 made in wire, which in particular comprise two end branches 106 each substantially orthogonal to the directions 10 and 15 and axially bearing against the two piston heads 56 respectively. The clip takes a general C shape, with the lower part of the C being formed by the two substantially parallel end branches 106, the upper part 108 of the C bearing axially against the upper surface of the rake 34 and the central part 110 of the C passing around the rake 34 in a direction orthogonal to the direction 10.

[0112] Thus, each clip 104 is made from deformed wire, allowing the application of a return force to the two adjacent piston heads 56, due to the general C shape of the clip and the two end branches 106 of the clip. Alternatively, each clip made in wire could maintain a general U shape, but would apply the return force to only one piston head 56.

Claims

1. A device (32) for a multichannel pipetting system, said device comprising: - a piston carrier (34) extending in a transverse direction (10) of the pipetting system; - a guide bar (38) for guiding the piston carrier, said guide bar extending parallel to a central longitudinal axis (14) of the pipetting system and orthogonally to the piston carrier (34); - a guide member (40) for guiding the guide bar (38) along the central longitudinal axis (14), said guide bar being slidably mounted in the guide member (40); - a plurality of pistons (20a, 20b) distributed along the piston carrier (34), each piston having a lower end slidably accommodated in a suction chamber (13a, 13b) and a piston head (56) mounted on the piston carrier via a mechanical connection (62) for mounting the piston (20a, 20b) on the piston carrier (34); - a row of sampling cone carrier ends distributed along the transverse direction (10) of the pipetting system, each end communicating with a respective one of the suction chambers (13a, 13b), characterized in that, for at least one of the pistons (20a, 20b), the mechanical connection (62) comprises two contact points (64a, 64b) which together define a rotation axis (66) of the piston head, said rotation axis being oriented orthogonally or substantially orthogonally to the transverse direction (10) and the central longitudinal axis (14) of the pipetting system, and in that the device further comprises elastic return means associated with the piston (20a, 20b) for forcing the piston head (56) upward against the piston carrier (34) for establishing the two contact points (64a, 64b).

2. The apparatus of claim 1, wherein, The elastic return means are formed by a substantially conical helical spring whose cross section tapers upward from the bottom, or by a spring in the form of a deformed wire.

3. The apparatus of claim 1 or claim 2, wherein, The piston carrier (34) has two opposite free transverse ends.

4. The apparatus of claim 1 or claim 2, wherein, The guide bar (38) is slidably mounted in the guide member (40) via two sliding pivotal connections spaced apart from each other along the central longitudinal axis (14).

5. The apparatus of claim 1 or claim 2, wherein, Each piston (20a, 20b) carries a seal (47) at its lower end, said seal being supported on an inner surface (49) of the suction chamber (13a, 13b) associated with the piston.

6. The apparatus of claim 5, wherein, The seal (47) is a lip seal.

7. The apparatus of claim 1 or claim 2, wherein, The two contact points (64a, 64b) of each mechanical connection (62) are symmetrically arranged about the associated piston axis (48a, 48b).

8. The apparatus of claim 1 or claim 2, wherein, The two contact points (64a, 64b) of each mechanical connection (62) are realized in either of the following ways: - using an annular surface provided on the piston and two flat surfaces provided on the piston carrier and inclined with respect to each other, - using a spherical surface provided on the piston and two flat surfaces provided on the piston holder and inclined relative to each other; - using a conical surface provided on the piston and two spherical surfaces provided on the piston holder; - using a flat surface provided on the piston and two spherical surfaces provided on the piston holder; - using a spherical surface provided on the piston and two spherical surfaces provided on the piston holder; - using a spherical surface provided on the piston and two cylindrical surfaces provided on the piston holder and having an axis of secant; or - using an annular surface provided on the piston and two cylindrical surfaces provided on the piston holder and having an axis of secant.

9. The apparatus of claim 1 or claim 2, wherein, The suction chambers (13a, 13b) have parallel chamber axes (50a, 50b).

10. The apparatus of claim 9, wherein, All the chamber axes (50a, 50b) are arranged in one and the same transversal plane of the pipetting system.

11. The apparatus of claim 9, wherein, The chamber axes (50a, 50b) are arranged in two separate parallel transversal planes (P1, P2) of the pipetting system in a staggered manner.

12. The apparatus of claim 11, wherein, The piston heads (56) are also arranged in the same two transversal planes (P1, P2) defined by the chamber axes (50a, 50b) in a staggered manner, so that these chamber axes coincide in pairs with the piston axes (48a, 48b).

13. The apparatus of claim 11, wherein, The piston heads (56) are all aligned along a transversal line (84) arranged parallel to and between the two transversal planes (P1, P2) defined by the chamber axes (50a, 50b), so that the piston axes (48a, 48b) are inclined relative to their corresponding chamber axes (50a, 50b).

14. The apparatus of claim 1 or claim 2, wherein, The piston holder (34) is made in two parts (34a, 34b) fixed to each other and between which the piston heads (56) and the elastic return means are arranged, or the piston holder (34) is made in one piece.

15. A multi-channel pipetting system comprising a device (32) according to any one of claims 1-14, the pipetting system being preferably a hand-operated, motorized or hybrid sampling pipettor, or a cartridge forming the lower part of an articulated arm intended to be connected to an automatic device.

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