A volumetric sampler designed to improve grip of the piston in the piston-capillary system

Abstract

The present invention relates to a volumetric sampling device (1) having a tip, an ejector, a fixture (15) fixed to the tip, and a movable pipette device (35) having a clamping system (34) for gripping the upper end of the piston. [Solution] A system (44) for controlling a clamping collar (40) of a clamping system is provided, the system (44) comprising elastic return means (46b) disposed between the collar (40) and the movable body (36), the system being designed such that, during the action of gripping the piston, upon axial movement of an instrument (35) which sets the body (36) in a predetermined axial position relative to a fixed body, the collar (40) is automatically moved from a relaxed high position to a clamped low position by the effect of the elastic return means (46b).

Description

[Technical field]

[0001] The present invention relates to the field of volumetric sampling devices, for example sampling pipettes, also called laboratory pipettes or liquid transfer pipettes. These are intended for sampling and dispensing liquids in containers etc. The present invention also relates to volumetric sampling devices in the form of automated devices. [Background technology]

[0002] As regards manual single-channel or multichannel pipettes, they are intended to be held by the operator in the hand during the operations of sampling and dispensing liquids, the movements of which are carried out by the application of axial pressure to a control button. As regards so-called positive displacement pipettes, they are intended to cooperate with piston-capillary type consumables, whose pistons are intended to be in direct contact with the sample to be taken before being expelled or reused. Thus, positive displacement pipettes have a different design from conventional air-displacement pipettes, whose pistons are an integral part of the pipette and are not in direct contact with the sample.

[0003] In a known manner, a capillary is intended to be attached to the tip of a pipette: the force holding the capillary at the tip should be high enough to ensure that the capillary does not fall off during pipetting, in particular during dispensing, and that this occurs independently of the viscosity of the liquid.

[0004] The upper end of the piston is also intended to be gripped by a clamping system comprising gripping members, such as fingers, with a ring for clamping these gripping members, which are typically translatable relative to the ring between a radially clamped position of the gripping members and a radially relaxed position of these same gripping members.

[0005] In the conventional case where the gripping members are able to translate and the ring surrounding them remains fixed, it remains difficult to achieve a very accurate and repeatable closure of the clamping system: in fact, this closure principle results in no precise control of the exact point on the piston end where the gripping members radially close during the axial movement.

[0006] Furthermore, this closure occurs regardless of the position of the piston in the capillary at the time the capillary is attached to the tip of the pipette, thus introducing another source of inaccuracy in gripping the piston and resulting repeatability problems.

[0007] To solve this problem, the operator must perform a self-calibration action intended to slide the upper end of the piston between the gripping members so that the piston is pressed securely against the bottom of the capillary tube. Apart from the fact that this self-calibration action may prove cumbersome when repeated by the operator and may give rise to comfort problems and possibly the appearance of musculoskeletal disorders (TMS), it also results in the need to provide a low clamping force of the piston sufficient to allow such sliding between the gripping members. This requirement is therefore in conflict with the requirement to provide for a secure grip of the piston to ensure the accuracy and proper implementation of the pipetting action.

[0008] These two conflicting requirements create difficulties in the design of pipettes. Similar problems are encountered in other types of sampling devices, such as automated devices. Summary of the Invention [Problem to be solved by the invention]

[0009] To address this problem, the object of the present invention is to a tip intended to support a capillary of a piston-capillary system, the tip being hollow and centered about a longitudinal central axis of the tip; an ejector intended to eject the piston-capillary system and movable relative to the tip according to an axial ejection stroke between a highest position at rest and a lowest position at ejection, the ejector having an ejection end intended to be in axial contact with the capillary end during the ejection stroke; A fixed body fixed to the tip portion; a movable pipette device capable of translational movement relative to a fixed body, the device comprising a movable body and a clamping system for gripping an upper end of a piston, the clamping system comprising gripping members fixed to the lower end of the movable body and a clamping ring of the gripping members, the ring itself being capable of translational movement relative to the gripping members between a radially clamped low position of the gripping members, in which the gripping members, biased radially inwards, can grip an upper end of a piston located between said gripping members, and a radially relaxed high position of the gripping members; A volumetric sampling device comprising: [Means for solving the problem]

[0010] According to the invention, the movable pipette instrument further comprises a piston drive member having a lower end intended to come into contact with the upper end of the piston during the action of gripping the piston with the capillary tube attached at its tip, the drive member being disposed between the gripping members and mounted for translational movement relative to the movable body between a maximum extension position and a minimum extension position, and first elastic return means for urging the drive member downwards relative to the movable body towards its maximum extension position.

[0011] The sample collection device further comprises a control system for the clamping ring of the clamping system, the control system comprising second elastic return means arranged between the clamping ring and the movable body, the control system being designed such that, during the action of gripping the piston, upon axial movement of the movable pipette device which brings the movable body into a predetermined axial position relative to the fixed body, the clamping ring automatically moves from its relaxed high position to its clamped low position under the effect of the second elastic return means.

[0012] Finally, during the axial movement of the movable pipette device, the drive member is moved towards its minimum protruding position relative to the movable body only after it comes into contact with the piston housed in the bottom of the capillary tube attached to the tip and counteracts the force generated by the first elastic return means, thereby making said predetermined axial position of the movable body available.

[0013] Thus, the present invention provides good repeatability since automatic closure of the piston clamping system is achieved by the following three features: - This only happens after the piston has been pressed against the bottom of the capillary. - by not moving the gripping members upwards, but instead by moving the clamping ring downwards around these gripping members. - at a specific point during the descent of the mobile pipetting instrument, when the mobile body reaches a defined axial position with respect to the fixed body.

[0014] Besides better repeatability of the pipetting action, the invention also provides comfort to the operator, since he no longer has to perform a self-calibration action after installation of each piston-capillary system in the tip, which can therefore result in faster pipetting actions, better efficiency and higher profitability.

[0015] Finally, it is also emphasized that while the present invention allows the ejection function to be transferred to a secondary system, in existing systems the ejection control is generally combined with the pipette control, resulting in the requirement of considerable force.

[0016] Preferably, the invention comprises at least one of any of the following features, considered separately or in any combination:

[0017] Preferably, the control system of the clamping ring comprises a member for holding the clamping ring in a relaxed high position, said holding member being connected to the clamping ring, and the control system also comprises a control part which is rotatably mounted on the movable body of the movable pipetting device according to a control part rotation axis, the control part comprising: a control finger intended to cooperate with a stop of the fixed body so as to pivot the control part relative to the mobile body according to a first direction of rotation about the control part rotation axis when the finger is pressed against the stop during a downward axial movement of the mobile pipetting device; a guide track of the holding member, which has a lateral blocking portion in which the holding member is held axially relative to the control part so as to hold the clamping ring in its high relaxed position relative to the gripping member, the guide track also having an axial sliding portion in which the holding member can slide during the automatic movement of the clamping ring from its high relaxed position towards its low tightened position under the effect of the second elastic return means, the lateral blocking portion and the axial sliding portion being connected to each other in a joint area in which the holding member is placed at a predetermined rotational level of the control part in a first rotational direction, caused by the control finger when the mobile body reaches its predetermined axial position relative to the fixed body, third elastic return means for forcing the control part to pivot relative to the mobile body according to a second direction of rotation about the axis of rotation of the control part, the second direction of rotation being opposite to the first direction; Equipped with:

[0018] Thus, the preferred technical solution described above allows automatic closure of the clamping system purely via mechanical elements, nevertheless, other solutions of a mechanical nature may also be envisaged, and may also comprise electrical and / or magnetic components, such as position sensors.

[0019] Preferably, the guide track has an overall L-shaped configuration.

[0020] Preferably, the control system for the clamping ring further comprises: a gear for driving the clamping ring from its low clamped position towards its high relaxed position, the gear being rotatably mounted on the control part; a connecting member, at one of its two ends, supporting the holding member and at its other end being eccentrically rotatably connected to the gear; an axially oriented rack supported on the ejector and intended to cooperate with a toothed wheel during the ejection movement of the piston-capillary system; Includes.

[0021] The above-mentioned means are advantageous since they allow the fastening system to be opened in a simple and reliable manner, requiring only a small space.

[0022] In this context, the control system of the clamping ring is preferably designed such that, during an ejection operation of the piston-capillary system in which the ejector performs a downward axial ejection stroke relative to its tip towards its lowest ejection position, the rack rotates the gear resulting in an upward movement of the connecting member and thus moving the retaining member upwards in the axial sliding part of the guide track which in turn drives the clamping ring towards its relaxed high position, and the third return elastic means is designed to force the control part to pivot relative to the movable body according to the second rotation direction so as to accommodate the retaining member at the bottom of the lateral blocking part of the guide track when the retaining member reaches the joining area of ​​the guide track.

[0023] Preferably, the control system of the clamping ring is designed such that pivoting of the control part relative to the movable body according to the second direction of rotation, under the action of the third elastic return means, causes separation of the gear from the rack and interruption of the cooperation between them.

[0024] In addition, the sampling device preferably also comprises a biasing means which, during the movement of the ejector between its highest rest position and its lowest ejection position, allows the rack to approach the mobile pipetting device from a given level of downward axial movement of the ejector, according to a direction transverse to the longitudinal central axis, making it possible to avoid unwanted cooperation between these two elements, particularly during pipetting operations with translational movement of the mobile pipetting device relative to the rack of the ejector, which remains fixed, when the biasing means are inactive and the rack then moves laterally away from the gear.

[0025] For example, the device may be a manual or motor-driven, single-channel or multi-channel, positive displacement sampling pipette, or a single-channel or multi-channel, positive displacement sampling automated device.

[0026] In the case where the sampler is of the multi-channel type, it is preferably provided with a common control system for simultaneously controlling several clamping rings, preferably all the clamping rings of the clamping system of the multi-channel sampler, Alternatively, a separate control system may be provided for each of the clamping systems of the multi-channel sampler without departing from the scope of the invention.

[0027] In the case where the sample collection device is of the single channel type, the retaining member of the clamping ring in the relaxed high position is preferably attached to the upper end of the clamping ring and is also preferably slidably received in an axial groove of the movable body of the movable pipette device.

[0028] Other advantages and features of the present invention will become apparent in the following non-limiting detailed description. [Brief description of the drawings]

[0029] The description will now be made with reference to the accompanying drawings. [Figure 1] 1 shows a perspective view of a positive displacement sampling pipette according to the present invention; [Diagram 2] FIG. 2 shows a partial longitudinal sectional view of a pipette according to the first preferred embodiment of the invention shown in the previous figure. [Diagram 3] FIG. 2 shows a perspective view of a portion of the pipette shown in the previous figure. [Figure 4] FIG. 2 shows a side view of the pipette shown in the previous figure. [Figure 5A] FIG. 5 shows a side view of a pipette similar to that of FIG. 4 during the operation of gripping the piston. [Figure 5B] 1 corresponds to a longitudinal section through a portion of the pipette shown in the previous figure. [Figure 6A]5B shows a side view of a pipette similar to that of FIG. 5A at a subsequent time in the act of gripping the piston. [Figure 6B] 1 corresponds to a longitudinal section through a portion of the pipette shown in the previous figure. [Figure 7] FIG. 6B shows a side view of a pipette similar to that of FIG. 6A at the end of the action of gripping the piston. [Figure 8] The diagram shows a side view of a pipette similar to that in Figure 4 during the ejection motion of the piston-capillary system. [Figure 9] The diagram in Figure 8 shows a side view of a pipette similar to that in Figure 8 at a subsequent time during the ejection movement of the piston-capillary system. [Figure 10] The diagram in Figure 9 shows a side view of a pipette similar to that in Figure 9 at a subsequent time during the ejection movement of the piston-capillary system. [Figure 11] The figure shows a side view of a pipette similar to that of Figure 10 at the end of the ejection stroke of the piston-capillary system. [Figure 12] FIG. 2 shows a longitudinal cross-sectional view of a multi-channel pipette according to a second preferred embodiment of the present invention, with the outer cover of the pipette removed to expose the inner elements of the pipette. [Figure 13] FIG. 2 shows a perspective view of a portion of the pipette shown in the previous figure. [Figure 14] FIG. 14 shows a perspective view of a portion of the pipette shown in FIGS. 12 and 13 at another viewing angle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] 1, there is shown a manually operated single channel positive displacement sampling pipette 1 according to the present invention. This manual pipette is also called a "mechanical pipette". Throughout the following description, the terms "high" and "low" should be considered with respect to the pipette being held vertically in or near the pipette operating position.

[0031] FIG. 1 shows a pipette 1 held in the hand 2 of an operator who uses his / her thumb 4 to manipulate the pipette to dispense a pre-aspirated liquid.

[0032] More specifically, the pipette 1 comprises a handle 6 forming the upper body of the pipette and exposing a pipette control rod 10. The pipette control rod carries at its upper end, in the pipette operating position, a control button 12 having an upper portion intended to receive the pressure of the operator's thumb 4.

[0033] It should be noted that, if necessary, a display screen (not shown) may be provided on the handle 6. Similarly, means for setting the volume to be sampled are also available to the operator on this handle 6.

[0034] Under the handle 6, the pipette 1 comprises a removable bottom part 14, which includes an outer stationary body 15. The outer stationary body 15 terminates downwards in a tip 16 which receives a consumable 18, the so-called piston-capillary system. In FIG. 1, only the capillary tube 21 of the system 18 is visible, since a piston is arranged inside the capillary tube 21 and the tip 16. In a known manner, the piston-capillary system 18 can be mechanically ejected after the pipetting operation, for example by means of an ejector 20 having an operating button 22 protruding from the top of the handle close to the control button 12. Between a maximum rest position shown in FIG. 1 and a minimum ejection position, the ejector 20 can be moved by an axial ejection stroke relative to the tip 16. In this regard, it should be noted that the ejector 20 comprises a lower ejection end 60 which is intended to be in axial contact with the upper end of the capillary tube 21 during the ejection stroke.

[0035] In a manner specific to the invention described below, the pipette control rod 10 is connected at its lower end to a clamping system (not shown in FIG. 1) that is capable of gripping and then releasing the upper end of the piston of the piston-capillary system 18.

[0036] 2-4, there is shown a portion of a pipette 1 according to a first preferred embodiment of the present invention, generally including the tip 16 and ejector 20 together with the inside of the bottom portion of the pipette.

[0037] 2 has a hollow shape centered on a central longitudinal axis 32 of the tip, which corresponds here to the central longitudinal axis of a single channel pipette. The hollow part of the tip 16 is intended to pass the piston 23 of the piston-capillary system 18, the upper end (23a) of which is gripped by a clamping system 34 actuated by the pipette control rod.

[0038] More specifically, the pipette comprises a movable pipette device 35 whose translation is controlled by a control rod (10) and a control button 12 shown in Figure 1. This movable pipette device 35 can thus be translated along an axis 32 relative to an outer fixed body 15 that surrounds it.

[0039] The tool 35 comprises in its upper part a mobile body 36 which is driven in translation by a control rod connected at its upper end. It also comprises a clamping system 34 for gripping the upper end 23a of the piston 23. This system 34 comprises gripping members 38, such as flexible fingers, fixed at the lower end of the mobile body 36. The system also comprises a ring 40 for clamping the fingers 38, which is arranged around the fingers 38 about the axis 32. The clamping ring 40 can then be translated along the axis 32 relative to the fingers 38 between a low radial clamping position of the fingers shown in FIG. 2, which allows the fingers biased radially inwards to grip the upper end 23a of the piston arranged between them, and a high radially relaxed position of the fingers shown in FIGS. 3 and 4. For example, as can be seen in FIGS. 2 and 3, the fingers 38 have a pointed head directed radially inwards. Since these fingers have tips that deform the plastic of the piston (which they clamp), this particular shape can counterbalance the closing control force by adding a more secure retention of the piston in the clamp. In this way it is possible to limit the retention force of the clamp in the closed position, which is ensured by the spring 46b, which must be compressed when the clamp opens to allow the piston-capillary ejection. This limits the force that the operator must exert. The movable pipette device 35 is completed by the piston drive member 42, best visible in Figure 2, and by a particular system 44 for controlling the clamping ring of the clamping system, best visible in Figures 3 and 4.

[0040] The piston drive member 42 has a lower end 42b intended to come into contact with the upper end 23a of the piston during the action of gripping the piston with the capillary tube attached to its tip, as will be described in detail below. The drive member 42 is arranged between the fingers 38. It is mounted so as to be able to translate along the axis 32 relative to these fingers and to the mobile body 36 which supports them, between a maximum projection position and a minimum projection position shown in FIG. 2. At its upper end 42a, the drive member 42 cooperates with a first elastic return means 46a of the compression spring type. This spring 46a urges the drive member 42 downwards towards its maximum projection position relative to the mobile body 36, against which it also abuts.

[0041] A system 44 for controlling the clamping ring 40 is unique to the present invention and is also described in detail below with reference to FIGS.

[0042] Firstly, the system 44 comprises a second elastic return means 46b, also of the compression spring type, arranged between the clamping ring 40 and the lower end of the mobile body 36. As will be explained in more detail later, the control system 44 is designed so that, during the action of gripping the piston 23, upon axial movement of the tool 35 which sets the mobile body 36 in a given axial position with respect to the fixed body 15, the clamping ring 40 moves automatically, under the effect of the second spring 46b, from its relaxed high position shown in Figures 3 and 4 to its clamped low position shown in Figure 2.

[0043] The control system 44 also comprises a member 50 for holding the clamping ring 40 in a high position when relaxed. This holding member 50 is fixedly or rotatably attached to the upper end 52 of the clamping ring. It has the form of an axis or shaft oriented transversely with respect to the central longitudinal axis 32 of the pipette, while the ends 52 of the clamping ring to which it is attached at its two ends are preferably in the form of two axial tabs arranged diametrically opposite each other around the mobile body 36.

[0044] The retaining member is also slidably received in an axial groove 54 in the mobile body 36, or in two diametrically opposed identical grooves in this body 36 which locally have a hollow shape.

[0045] Furthermore, the control system 44 includes a control part 60 mounted on the mobile body 36 so as to be rotatable according to a rotation axis of the control part 62 parallel to the holding member 50. The control part 60, which is of flat or substantially flat shape, comprises several elements intended to perform several functions.

[0046] Firstly, the control part 60 comprises an eccentric control finger 64 intended to cooperate with an axial stop 66 of the fixed body 15, for example formed by an inner sectioning of the fixed body 15. The assembly is designed such that, during a downward axial movement of the instrument 35, the abutment of the eccentric finger 64 on the axial stop 66 (shown in FIG. 4 ) causes the control part 60 to pivot relative to the mobile body 36 according to a first rotation direction S1 about the axis of rotation 62.

[0047] The control part 60 also comprises a guide track 68 for the retaining member 50. In this first preferred embodiment of the invention, the guide track 68 is provided by a hole or groove having an overall shape of an L-shape directed downwards. The guide track 68 has a lateral blocking portion 70 in which the retaining member 50 is axially held relative to the control part 60. The lateral portion is straight or slightly curved and is oriented laterally or substantially laterally relative to the axis 32. It may, for example, consist of a portion corresponding to a circular arc of small amplitude, centered on the rotation axis 62 of the control part 60. The retention of the retaining member 50 at the bottom 70a of the lateral blocking portion 70 ensures the retention of the tightening ring in its relaxed high position. The bottom 70a of the lateral blocking portion 70 corresponds to the distal end of this portion considered in the above-mentioned first rotation direction S1. In order to press the retaining member 50 against the bottom 70a, a third elastic return means 46c is provided, which is arranged between the mobile body 36 and the control part 60. In fact, this third elastic return means 46c, preferably in the form of a spring, causes the control part 60 to pivot relative to the movable body 36 according to a second rotational direction S2 about the rotation axis of the control part 62, the second direction S2 being opposite to the first direction S1.

[0048] The guide track 68 also has an axial sliding portion 72 along which the retaining member 50 slides from its high relaxed position towards its low tightened position during the automatic movement of the clamping ring 40. The axial sliding portion 72 is oriented parallel to the axis 32 or at a small angle with respect to this axis, depending on the development of the inclination of the control part 60 during operation. This portion 72 thus extends downwards from the other end of the lateral blocking portion 70, so that the two portions 70, 72 are connected to one another at a joint area 74, which corresponds to the joint between the base and the branches of the L.

[0049] The control system 44 of the clamping ring 40 further comprises a gear 76 for driving the clamping ring from its low clamped position towards its high relaxed position. The gear 76 is mounted on the control part 60 for rotational movement according to a gear rotation axis 77 parallel to the axis 62. As engaging with the gear 76, the control system 44 also comprises a rack 80 axially oriented and supported on the ejector 20. As will be explained in more detail below, the rack 80 is intended to cooperate with the gear 76 during the ejection movement of the piston-capillary system 18. It should be noted that the pipette further comprises a deflection means 82, such as a deflection pin, capable of moving the rack 80 closer to the instrument 35 from a given level of downward axial movement of the ejector 20. The operation of this deflection pin 82, which is shown diagrammatically in FIG. 3, will be explained later in this specification.

[0050] The system 44 also incorporates a connecting member 78 in the form of an arm which at one of its ends fixedly or pivotably supports the holding member 50. At the other end, the arm 78 is eccentrically connected to the gear 76, while it is rotatably attached to the gear according to an arm rotation axis 79 parallel to the axis 77.

[0051] 2 to 7, the different steps of the operation of gripping the piston with the capillary tube 21 attached to the tip 16 and abutting against the support of the work surface will now be described. The gripping operation is of an automatic nature, initiated following the downward movement of the movable instrument 35 via a button or control rod.

[0052] Before the downward movement of the device 35, the piston is in any position of the capillary, i.e. not necessarily at the bottom 21a of the capillary here, which corresponds to the reduced cross-section at the end of the small-diameter hollow rod in which the piston slides (hydraulic part of the piston-capillary system). Alternatively, the bottom may correspond to the lower end of the capillary, depending on the design of the piston-capillary system, and may be usually conical in shape and intended to cooperate with the lower end of the piston. Preferably, this design is adopted when there is no collar at the bottom of the upper end of the piston.

[0053] Also, as shown in FIG. 3, the clamping ring 40 is held in a high position when relaxed via a retaining member 50.

[0054] During the axial movement of the mobile tool 35, the control finger 64 comes into contact with the axial stop 66 of the fixed body 15 and then pivots the control part 60 in a first direction S1 around the axis 62. The start of this pivoting phase of the control part 60 is diagrammatically illustrated in Figures 5A and 5B. This pivoting of the control part 60 results in a relative movement of the control member 50 in the lateral blocking portion 70 of the guide track 68. Given the lateral orientation of the portion 70, the retaining member 50 continues to hold the clamping ring 40 in its relaxed high position. During the downward movement of the tool 35, if the maximum protruding position of the piston has not yet been taken at the start of the gripping movement, the piston drive member 42 in this position comes into axial contact with the upper end 23a of the piston and moves it towards the bottom 21a of the capillary. Thus, an abutment can be observed between the collar 23b of the piston, which is arranged below the upper end 23a, and the capillary bottom 21a. For the sake of clarity, it is pointed out that the collar 23b is conventionally disposed axially between the upper end 23a of the piston and the lower end of the piston which slides within the thin hollow rod of the capillary tube 21.

[0055] Upon continued downward axial movement of the movable pipette device 35, pressure on the drive member 42 against the piston housed in the capillary bottom 21a moves said member 42 towards a minimum protruding position relative to the movable body 36, against the force exerted by the first spring 46a.

[0056] This relative movement of the drive member 42 constitutes a kind of safety device making it possible to ensure that the piston 23 is properly accommodated in the bottom 21a of the capillary tube 21 upon closure of the clamping system intended to grip the piston. To obtain such a function it is therefore essential that the frictional force of the piston moving in the capillary tube is lower than the return force provided by the first spring 46a.

[0057] After the start of the relative movement of the drive member 42 towards the minimum protruding position, the continued descent of the instrument 35 causes the mobile body 36 to reach a predefined axial position with respect to the fixed body 15, as shown in Figures 6A and 6B. This specific position of the mobile body 15 also causes the setting of the control part 60, due to the rotation applied by the finger 64, at a predefined rotation level according to the first direction S1 about the axis 62. This rotation level is such as to set the retaining member 50 at the end of the lateral blocking portion 70 of the guide track 68 in the joining area 74.

[0058] It is at this point that automatic closure of the clamping system occurs due to the effect of the second spring 46b which can expand and press the ring 40 around the fingers 38. This movement of the ring 40 is made possible by the retaining member 50 being free to move downwardly in the axial sliding portion 72 of the guide track 68 to the lower end of said portion 72, as shown in Figure 7 with the ring 40 in its clamped low position. At the same time that the retaining member 50 moves in the axial sliding portion 72 of the guide track 68, it also slides downwardly in the axial groove 54 of the movable body 36.

[0059] Finally, it should be noted that during rotation of the control part 60, the gear 76 carried by this part 60 is laterally offset, so that the control part 60 moves away from the axis 32 so as to assume a position suitable for subsequently carrying out the ejection action of the piston-capillary system, as will now be described in more detail below with reference to Figures 8 to 11.

[0060] Such ejection action begins with the relaxation of the clamping system, which causes the ring 40 to move upwards in its relaxed high position in order to release the piston head 23a. To do this, the ejector 20 is operated by the operator. When this ejector reaches a certain level of downward axial movement, as shown diagrammatically in FIG. 8, its continued descent brings it into contact with a biasing pin 82, which moves the rack 80 laterally closer to the axis 32. For example, a cam track 83 provided at the rear of the rack can be used to obtain the desired lateral deflection in cooperation with the biasing pin 82. In fact, this observed deflection brings the teeth of the rack 80 into engagement with the teeth of the gear 76, as can be seen in FIG. 9.

[0061] The continued downward movement of the ejector 20 therefore rotates the gear 76 and drives upwards the arm 78 eccentrically attached to said gear 76. By its upward movement, the arm 78 causes an upward movement of the retaining member 50 in the axial sliding portion 72 and drives the ring 40 therewith towards its released axial position visible in Fig. 10. Indeed, in this position, the retaining member 50 is brought to its highest position with respect to the mobile body 36 by fitting into the interface area 74 of the guide track.

[0062] At this stage, the third elastic return means 46c are stretched, forcing the control member 60 to pivot according to the second direction S2 relative to the mobile body 36, thereby receiving the retaining member 50 in the bottom 70a of the lateral blocking portion 70 of the guide track. As can be seen in Fig. 11, the clamping ring 40 is thus secured in its relaxed high position, thereby releasing the piston 23 of the piston-capillary system to be ejected.

[0063] Lifting of the clamping ring 40 is performed by loading the second spring 46b and compressing it between the ring 40 and the movable body 36. This is done so that the restoring force of this spring 46b is therefore lower than that of the pipette spring (not shown) which forces the entire movable instrument 35 upwards.

[0064] Following the pivoting of the control part 60 under the action of the third elastic return means 46c, the gear 76 again leaves the rack 80 by approaching the axis 32. As a result of this, the cooperation between the gear 76 and the rack 80 is interrupted and the rack is driven downwards together with the ejector 20 until it abuts against the capillary tube and causes it to fall out of the tip of the pipette. During this falling out (not shown), the capillary tube is expelled from the pipette together with the piston, which had previously been released from its clamping part.

[0065] Once the evacuation of the piston-capillary system is complete, the ejector 20 is released by the operator, which then rises under the action of a dedicated spring (not shown), also in cooperation with the deflection pin 82 .

[0066] Although the first embodiment described above corresponds to a single channel pipette, the invention also applies to multi-channel pipettes, such as in the second embodiment described below with reference to Figures 12 to 14.

[0067] In the figures, elements with the same reference numbers correspond to identical or similar elements. It can be seen that, consequently, in the multichannel pipette 1, several, here eight, tips 16 are provided. To simultaneously control the eight clamping rings 40, a control system 44 common to all these rings is preferably provided and is preferably mounted in the center of the pipette, between the two series of four tips. Here, the holding member 50 is connected at its two ends to a mobile axial rail 84, which is fastened at its upper end to a transverse ramp 86 that slidably supports two axial tie rods 88 that traverse the mobile body 36. At the lower ends of these tie rods 88, an axial stop 90 holds the collar of the upper part of each clamping ring 40. In turn, a second return spring 46b is arranged between the lower end of the mass body 36, traversed by the tie rods 88, and the collar of the associated ring 40. The above-mentioned elements 84 , 86 , 88 , 90 form a kinematic chain that can relate the movement of the clamping ring 40 to the movement of the retaining member 50 .

[0068] Finally, it should be noted that the control finger 64, which is best visible in FIG. 13, cooperates with an axial stop 66 formed in a fixing member 92 mounted on the inside of the pipette.

[0069] It goes without saying that various modifications may be made by those skilled in the art to the invention described so far only as a non-limiting example, the scope of which is defined by the appended claims. In particular, although the preferred embodiment described above corresponds to the implementation of the invention on a manual pipette, all teachings may be applied to other types of pipettes, which may be motor-driven and / or multi-channel, or to automated devices. [Explanation of symbols]

[0070] 1 Pipette 2 Hands 4 Thumbs 6 Handle 10 Pipette Control Rod 12 Control Buttons 14 Bottom part 15 Outer fixation body 16 Tip 18 Piston-Capillary System 20 Ejector 21 Capillary 21a Capillary bottom 22 Operation buttons 23 Piston 23a Top end / piston head 23b Color 32 Vertical center axis 34 Fastening System 35 Movable pipette device 36 Movable body 38 Gripping member / fingers 40 Tightening ring 42 Piston drive member 42a Upper end 42b Bottom end 44 Control System 46a First elastic return means 46b Second elastic return means 46c Third elastic return means 50 Retaining member 52 Upper end 54 Axial groove 60 Control parts 62 Control part rotation axis 64 Control Finger 66 Axial Stop 68 Guide Truck 70 Lateral blocking part 70a bottom 72 Axial sliding part 74 Joint Area 76 Gears 77 Gear rotation axis 78 Connection parts 79 Arm rotation axis 83 Cam Track 80 racks 82 Deflection means 84 Movable axial rail 86 Landscape Lamp 88 Axial tie rod 90 Axial Stop 92 Fixing member S1 1st rotation direction S2 Second rotation direction

Claims

1. a tip (16) intended to support a capillary (21) of a piston-capillary system (18), the tip being hollow and centered on a central longitudinal axis (32) of the tip; an ejector (20) intended to eject the piston-capillary system (18) and movable relative to the tip (16) according to an axial ejection stroke between a highest rest position and a lowest ejection position, the ejector (20) having an ejection end (60) intended to be in axial contact with the end of the capillary tube (21) during the ejection stroke; a fixed body (15) fixed to the tip portion (16); a movable pipette device (35) capable of translational movement relative to the fixed body (15), comprising a movable body (36) and a clamping system for gripping the upper end of a piston, the clamping system (34) comprising gripping members (38) fixed to the lower end of the movable body (36) and a clamping ring (40) of the gripping members, the clamping ring (40) itself being capable of translational movement relative to the gripping members (38) between a radially clamped low position of the gripping members, which allows the gripping members, biased radially inward, to grip the upper end (23a) of the piston located between the gripping members (38), and a radially relaxed high position of the gripping members; A positive displacement sampler comprising: The movable pipette device (35) further comprises a piston drive member (42) having a lower end (42b) intended to come into contact with the piston upper end (23a) during the operation of gripping the piston with the capillary tube attached to the tip, the drive member (42) being disposed between the gripping members (38) and mounted for translational movement relative to the movable body (36) between a maximum protrusion position and a minimum protrusion position, and first elastic return means (46a) for urging the drive member (42) downwards relative to the movable body (36) towards its maximum protrusion position, the volumetric sampling device further comprises a control system (44) for the clamping ring (40) of the clamping system, the control system (44) comprising second elastic return means (46b) arranged between the clamping ring (40) and the movable body (36), the control system being designed so that, during the action of gripping the piston (23), upon axial movement of the movable pipette device (35) which brings the movable body (36) into a predetermined axial position relative to the fixed body, the clamping ring (40) automatically moves from its relaxed high position to its clamped low position by virtue of the second elastic return means (46b); During the axial movement of the movable pipette device (35), the drive member (42) moves towards its minimum protruding position relative to the movable body (36) only after it abuts against the piston (23) housed in the bottom (21 a) of the capillary tube attached to the tip and counteracts the force generated by the first elastic return means (46 a) so that the predetermined axial position of the movable body (36) is available. Volumetric sampler.

2. the control system (44) of the clamping ring (40) includes a holding member (50) for holding the clamping ring (40) in the relaxed high position, the holding member (50) being connected to the clamping ring (40), and the control system also includes a control part (60) mounted on the movable body (36) of the movable pipette device (35) so as to be rotatable according to a control part rotation axis (62); The control component (60) a control finger (64) intended to cooperate with a stop (66) of the fixed body (15) in such a way that, during the downward axial movement of the movable pipetting device (35), pressing the control finger (64) against the stop (66) causes the control part (60) to pivot relative to the movable body (36) according to a first direction of rotation (S1) about the control part rotation axis (62); a guide track (68) of the retaining member (50), the guide track having a lateral blocking portion (70) by which the retaining member (50) is axially held relative to the control part (60) so as to hold the clamping ring (40) in its high relaxed position relative to the gripping member, the guide track (68) also having an axial sliding portion (72) by which the retaining member (50) can slide from its high released position towards its low clamped position under the effect of the second elastic return means (46b) during automatic movement of the clamping ring (40), the lateral blocking portion (70) and the axial sliding portion (72) being connected to each other at a joint area (74) in which the retaining member (50) is placed at a predetermined rotation level of the control part (60) in the first rotation direction (S1) caused by the control finger (64) when the movable body (36) reaches its predetermined axial position relative to the fixed body, third elastic return means (46c) for forcing the control part (60) to rotate relative to the movable body (36) in a second direction of rotation (S2) about the axis of rotation of the control part (62), said second direction of rotation being opposite to the first direction; 10. The positive displacement sampler of claim 1, comprising:

3. 3. The positive displacement sampler of claim 2, wherein the guide track (68) has an overall L-shaped configuration.

4. The control system (44) of the clamping ring (40) further comprises: a gear (76) for driving the clamping ring (40) from its low clamped position to its high released position, the gear (76) being rotatably mounted on the control component (60); a connecting member (78) that supports the holding member (50) at one of its two ends and is eccentrically rotatably connected to the gear (76) at the other end; an axially oriented rack (80) supported on said ejector (20), said rack (80) intended to cooperate with said gear (76) during the ejection movement of said piston-capillary system (18); 4. A volumetric sampling device according to claim 2 or 3, comprising:

5. The control system (44) of the clamping ring (40) controls the rack (80) to rotate the gear (76) and consequently cause the connecting member (78) to move upward, thereby moving the retaining member (50) upward in the axial sliding portion (72) of the guide track, during the ejection operation of the piston-capillary system (18) in which the ejector (20) performs an axial downward ejection stroke relative to the tip end toward its lowest ejection position.

5. A volumetric sampling device according to claim 4, wherein the third elastic return means (46c) are designed to force the control part (60) to pivot relative to the movable body (36) in the second direction of rotation (S2) so as to also drive the clamping ring (40) towards its high position when relaxed and to accommodate the retaining member (50) in the bottom (70a) of the lateral blocking portion (70) of the guide track when the retaining member (50) reaches the joining area (74) of the guide track.

6. 6. A volumetric sampling device according to claim 5, wherein the control system (44) of the clamping ring (40) is designed in such a way that pivoting of the control part (60) relative to the mobile body (36) in the second direction of rotation (S2), under the action of the third elastic return means (46c), causes separation of the toothed wheel (76) from the rack (80) and interruption of the cooperation between them.

7. 5. A volumetric sampling device according to claim 4, comprising a biasing means (82) for enabling the rack (80) to approach the movable pipette device (35) from a predetermined level of downward axial movement of the ejector (20) in a direction transverse to the longitudinal central axis (32) during movement of the ejector between its highest rest position and its lowest ejection position.

8. 4. A volumetric sampler according to any one of claims 1 to 3, which is a manual or motor-driven, single-channel or multi-channel pipette or an automated volumetric sampler.

9. 4. A volumetric sampling device according to any one of claims 1 to 3, being of the multi-channel type and comprising a common control system (44) for simultaneously controlling several clamping rings (40), preferably all of the clamping rings (40) of the clamping system (34) of the multi-channel sampling device.

10. 4. A volumetric sampling device according to claim 2 or 3, which is of a single channel type and wherein a retaining member (50) of the clamping ring (40) in the relaxed high position is attached to an upper end of the clamping ring and is preferably slidably received in an axial groove (54) of the movable body (36) of the movable pipette device (35).

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