Positive displacement sampling device designed to facilitate capillary ejection

Abstract

The invention relates to an assembly (30) for a positive displacement sampling device, the assembly comprising a tip (16) and an ejector (20), the tip (16) comprising a body (42), a mobile capillary retention portion (44) connected to the body (42) by a connector, and a lever (54) secured to the mobile portion, such that moving this portion radially inwards, via the connector, leads to the lever (54) moving radially outwards, the ejector (20) being equipped with a locking member (64) which engages with the lever (54) such that, in the top position of the ejector (20), the locking member (64) assumes a locking position in which it holds the mobile portion (44) in an active capillary retention position by preventing the lever (54) from moving radially outwards and, during the ejection travel, the locking member (64) permits the lever (54) to move radially outwards.

Description

[0001] The present invention relates to the field of positive displacement sampling devices, for example sampling pipettes, also known as laboratory pipettes or liquid transfer pipettes. These are intended for sampling and dispensing liquid into containers or the like. The invention also relates to automated positive displacement sampling devices.

[0002] Manual pipettes, whether single-channel or multi-channel, are designed to be held by an operator during liquid sampling and dispensing operations. These operations are performed by moving a control knob, which is activated by applying axial pressure to the knob. Positive displacement pipettes, on the other hand, are designed to work with piston-capillary systems, where the piston is intended to come into direct contact with the sample before being ejected or reused. Positive displacement pipettes therefore have a different design than more conventional air-displacement pipettes, in which the piston is an integral part of the pipette and does not come into direct contact with the sample.

[0003] As is well known, the capillary tube is designed to be fitted onto a pipette tip. The force required to hold the capillary onto the tip must be sufficient to ensure that it does not come loose during pipetting operations, particularly during dispensing, regardless of the liquid's viscosity. These requirements necessitate a firm axial fit of the capillary onto the pipette tip, resulting in the capillary becoming increasingly difficult to eject as the insertion force increases.

[0004] This ambivalent situation poses a problem in terms of the ergonomics of the piston-capillary ejection system. Indeed, the operator may have to exert significant force to generate the desired ejection using the ejector integrated into the pipette. This can lead to comfort issues, as well as the development of musculoskeletal disorders (MSDs).

[0005] Similar problems are encountered in devices, such as automated systems, that provide motorized ejection of the piston-capillary system, since the ejection motor must be sufficiently powerful to counteract the force exerted by the capillary's insertion onto the nozzle, thereby breaking the mechanical connection between the two. It should be noted that these problems are exacerbated in multichannel designs.

[0006] US 4 418 580, FR 3 003 643, US 9 360 493 and US 2020 / 215529 describe other known examples of positive displacement sampling devices including a capillary ejection system.

[0007] To address this problem, the invention relates to an assembly for a positive displacement sampling device, the assembly comprising: an end fitting intended to carry a capillary of a piston-capillary system, the end fitting being hollow, centered on a longitudinal central axis of the end fitting, and having an outer surface provided with an axial capillary retention element, an ejector intended to eject the piston-capillary system, the assembly being designed so as to allow an axial ejection stroke of the ejector relative to the end fitting, between an extreme high rest position and an extreme low ejection position, the ejector comprising an ejection end intended to be in axial contact with a capillary end during the ejection stroke.

[0008] According to the invention, the nozzle comprises a body and a movable capillary retention portion connected to the body by a linkage, the movable retention portion having on its outer surface at least a part of said axial capillary retention element, the nozzle also comprising a lever integral with the movable retention portion, such that a radial inward tilting of the movable portion, via the linkage and relative to the nozzle body, causes the lever to tilt radially outward, the ejector being equipped with a locking element cooperating with the lever such that: In the extreme high rest position of the ejector, the locking member occupies a locked position in which it maintains the movable portion of the nozzle in an active capillary retention position, preventing the lever from tilting radially outwards; and during the ejection stroke of the ejector, the locking member: allows the lever to tilt radially outwards, resulting from a tilting of the movable portion radially inwards from its active capillary retention position, to a retracted capillary release position, or causes the lever to tilt radially outwards, leading to a tilting of the movable portion radially inwards from its active capillary retention position, to its retracted capillary release position.

[0009] The invention thus provides for functionalizing the tip by adopting a segmented / split design that allows it to satisfactorily address the ambivalent situation described above. Indeed, thanks to the invention, the movable retention portion integrated into the tip can be maintained in its active position of retaining the capillary during pipetting operations, thereby ensuring a firm connection of the capillary to the tip. Furthermore, the ability of this same movable retention portion to retract into its retracted position for capillary release significantly reduces the force required on the ejector to disengage and eject the piston-capillary system.

[0010] Finally, it is emphasized that the invention also allows the ejection function to be moved to a secondary system, whereas in existing systems, the ejection control is generally combined with the pipetting control, resulting in significant effort.

[0011] The invention preferably has at least one of the following optional features, taken individually or in combination.

[0012] Preferably, within the nozzle, the connection between the mobile portion for capillary retention and the nozzle body is a flexible, elastically deformable connection.

[0013] Preferably, the tip has an intermediate crown centered on its longitudinal central axis, and the flexible connection is made by two flexible zones of reduced thickness, between which are delimited a first angular sector of crown as well as a second angular sector of crown, the first angular sector being integral with the mobile portion of capillary retention and the lever by being arranged between the two, while the second angular sector is integral with the body of the tip.

[0014] Preferably, the two flexible zones of reduced thickness are diametrically opposed.

[0015] Preferably, the tip also includes a fixing plate, attached to the second angular sector of the crown.

[0016] Preferably, the tip is made from a single piece, although alternatively, a design in several pieces assembled together can be envisaged, without departing from the scope of the invention.

[0017] Preferably, the locking member provided on the ejector is made by a radial stop member, intended to cooperate with an inclined plane of the lever of the nozzle.

[0018] According to an alternative to the flexible connection described above, the connection between the mobile capillary retention portion and the nozzle body can be a pivot connection or a ball joint connection.

[0019] Preferably, the mobile capillary retention portion has a general half-cylinder shape.

[0020] Preferably, another part of said axial capillary retention element is provided on the outer surface of the nozzle body.

[0021] In this regard, it is noted that the axial capillary retention organ is preferentially made using at least one annular ridge on the outer surface of the tip.

[0022] Preferably, the mobile capillary retention portion and the nozzle lever are made of a single piece, regardless of the design chosen for the connection between the mobile retention portion and the nozzle body.

[0023] The invention also relates to a positive displacement sampling device comprising at least one such assembly. For example, this device is a manual or motorized, single-channel or multi-channel positive displacement sampling pipette, or an automated single-channel or multi-channel positive displacement sampling device.

[0024] Other advantages and features of the invention will appear in the detailed, non-limiting description below.

[0025] The description will be made with reference to the attached drawings, among which are; [ Fig. 1 ] represents a perspective view of a positive displacement sampling pipette, according to the invention; [ Fig. 2 ] represents a partial longitudinal cross-sectional view of the pipette shown in the preceding figure, showing in particular an assembly according to a first preferred embodiment of the invention; [ Fig. 3 ] represents a perspective view of the pipette tip belonging to the assembly shown in the previous figure; [ Fig. 4 ] represents a side view of the tip shown in the previous figure; [ Fig. 5 ] represents a partial longitudinal cross-sectional view similar to that of the figure 2 showing the assembly at a given moment during an ejection operation of the piston-capillary system; [ Fig. 6 ] represents a perspective view of the tip, in its state as adopted at the given moment represented on the figure 5 ; Fig. 7 ] represents a partial longitudinal cross-sectional view similar to that of the figure 5 , at the end of the piston-capillary system ejection operation; and [ Fig. 8 ] represents a side view of the assembly, according to a second preferred embodiment of the invention.

[0026] With reference first and foremost to the figure 1 A single-channel, positive-displacement, manually operated sampling pipette 1, according to the present invention, is shown. This manual pipette is also referred to as a "mechanical pipette." Throughout the following description, the terms "up" and "down" refer to the pipette held vertically, in the pipetting position or close to it.

[0027] On the figure 1 , it is represented the pipette 1 held by the hand 2 of an operator, who, with the help of his thumb 4, operates the pipette to generate the distribution of a liquid which has previously been aspirated.

[0028] More specifically, the pipette 1 includes a handle 6 forming the upper body of the pipette, from which a pipetting control rod 10 opens. This rod has at its upper end, in the pipetting position, a control button 12 whose upper part is intended to be subjected to the pressure of the operator's thumb 4.

[0029] For information purposes, it is noted that a display screen (not shown) may be provided on handle 6. Similarly, means for adjusting the volume to be taken are also accessible to the operator on this handle 6.

[0030] Under the handle 6, the pipette 1 has a removable lower part 14, including an outer body 15 of the lower part. The lower part 15 terminates downwards in a nozzle 16 receiving a consumable 18, called a piston-capillary system. On the figure 1 , only the capillary 21 of the system 18 is visible, since the piston is located inside the capillary 21 and the tip 16. In a known manner, after pipetting, the piston-capillary system 18 can be mechanically ejected by an ejector 20 whose actuation button 22 is located for example in projection on the top of the handle, near the control button 12.

[0031] The pipetting control rod 10 is connected at its lower end to a clamping system (not visible on the figure 1 ), capable of gripping and then releasing the piston of the piston-capillary system 18, in a known manner which will not be described here.

[0032] Now, referring to figures 2 à 4 , it is represented as an assembly 30 according to a first preferred embodiment of the invention, this assembly being integrated into the pipette shown on the figure 1 , and comprising overall the tip 16 and the ejector 20 of particular designs.

[0033] Tip 16, the most visible on the figures 3 And 4 The tip has a hollow shape, being centered on a longitudinal central axis 32 of the nozzle, corresponding here to the longitudinal central axis of the single-channel pipette. The hollow of the nozzle 16 is designed to be traversed by the piston 23 of the piston-capillary system 18, the upper end of which is gripped by the clamping system 34 driven by the pipetting control rod.

[0034] The outer surface 36 of the nozzle 16 is provided with an axial retention element 38 for the capillary, formed by an annular ridge centered on the axis 32, or alternatively in the form of a shoulder or any similar shape. In all cases, the element 38 constitutes an axial stop intended to retain the capillary 21 on the nozzle 16. In a known manner, the inner surface of the upper part of the capillary is shaped to cooperate with the axial retention element 38 of the nozzle, for example by having an annular projection 40 extending radially inwards, housed in a recess 41 of the nozzle delimited at its lower end by the element 38.

[0035] More specifically, the axial capillary retention element 38 does not extend continuously around the outer surface 36 of the tip, since the latter has a segmented / slotted design specific to the invention, which will be described below. The element 38 therefore has the same segmented / slotted design in the circumferential direction.

[0036] The main part of the nozzle 16 is not entirely cylindrical, as it is segmented between a nozzle body 42 and a movable capillary retention portion 44. The nozzle body 42 is fixed, its upper part 42a having a general half-cylinder shape, while its lower part 42b has a general full-cylinder shape. The two parts are arranged axially in line with each other and are preferably made from a single piece, i.e., a single block or a single unit. The material used is preferably a plastic, or for example, overmolded aluminum.

[0037] The hollowed-out portion of the nozzle body 42, opposite its upper part 42a, is occupied by the movable retention portion 44, which is also preferably generally semi-cylindrical in shape. Together, the nozzle body 42 and the movable retention portion 44 form a conventional nozzle, except that a space 46 separates them circumferentially and axially, resulting in the aforementioned segmented / slotted design.

[0038] The ridge or shoulder 38 is located partly on the outer surface of the nozzle body 42, and partly on the outer surface of the movable retention portion 44. The two elements 42, 44, which together constitute a large part of a cylinder centered on the axis 32, are connected to each other at their upper end by means of an intermediate ring 50, also centered on the axis 32.

[0039] This crown 50 incorporates a flexible connection between the tip body 42 and the movable retention portion 44, in the form of two thin, diametrically opposed flexible zones 52. Between these two flexible zones 52, a first angular sector of the crown 50a is defined, integral with the movable retention portion 44, and, opposite it, a second angular sector of the crown 50b is defined, integral with the tip body 42. The flexible connection allows, through elastic deformation of the two flexible zones 52, a pivoting movement of the two angular sectors of the crown 50a, 50b relative to each other, along a transverse pivot axis passing through these two flexible zones 52.

[0040] Here again, the intermediate crown 50 is preferably made in one piece with the elements 42, 44 of the tip.

[0041] Extending upwards from the movable retention portion 44, starting from the first angular sector of the crown 50a, the tip is completed by a lever 54. The first angular sector of the crown 50a is thus arranged between the movable portion 44 and the lever 54, along the direction of the axis 32. The elements 44, 50a, and 54 thus form a rigid assembly, preferably made from a single piece, designed to minimize deformation during use of the pipette. Conversely, to ensure the operation described below, a certain rigidity is required so that this assembly can move without deforming, and in particular to ensure that a radial inward tilting of the movable retention portion 44, via the connection 52, and relative to the tip body 42, results in a radial outward tilting of the lever 54.

[0042] Finally, the tip 16 is completed by a fixing plate 56 extending upwards from the second angular sector of the crown 50b. The plate 56, arranged diametrically opposite the lever 54, constitutes a fixed part of the tip which is intended to be fixed directly or indirectly on the outer body 15 of the lower part of the pipette.

[0043] Ejector 20, visible on the figure 2 , is designed to eject the piston-capillary system 18 by axial pressure on the upper end of the capillary 21. The pipette allows an axial ejection stroke of the ejector 20 relative to the tip 16, between an extreme upper rest position shown on the figure 2 , and an extremely low ejection position shown on the figure 7 which will be described later. To this end, the ejector 20 includes a lower ejection end 60 intended to be in axial contact with an upper capillary end during the ejection stroke. As is known, the lower ejection end 60 of the ejector, centered on the axis 32, can have a large circumferential extent, exceeding, for example, 180°.

[0044] The ejector 20 and the lever 54 are designed to cooperate together to maintain a firm fit of the capillary 21 onto the tip 16 during pipetting, while limiting the effort required on the ejector 20 to cause the ejection of the piston-capillary system 18.

[0045] Thus, the lever 54 has, in its upper part, a radially external cam surface 62, the shape of which is such that this surface 62 moves radially upwards from the axis 32. The cam surface 62 can therefore be an inclined plane, or alternatively a curved surface.

[0046] Furthermore, to cooperate with the cam surface 62 of the lever 54, the ejector 20 is equipped with a locking member 64, which here corresponds to an axial stop member. In the extreme upper rest position of the ejector 20, as shown in the figure 2 The locking member 64 occupies a locked position in which it is in contact with the cam surface 62, arranged radially outwards relative to it. As a result, the locking member 64 prevents the lever 54 from pivoting radially outwards and maintains the lever in an upright position, thus helping to keep the movable retaining portion 44 in an active capillary retention position. The active retention position of the movable portion 44, as shown in the figure 2 This also corresponds to an upright position of the movable retention portion 44, in which it optimally reconstitutes the cylinder with the fixed tip body 42. In other words, in this active retention position, the portion of the bead 38 located on the outer surface of the movable retention portion 44 is arranged in its most eccentric position relative to the axis 32, which allows it to help firmly hold the capillary 21 onto the tip. Locking the movable retention portion 44 in this position, by the radial support between the elements 62 and 64, thus allows pipetting operations without risk of breaking the connection between the tip and the capillary. After pipetting, when the ejection stroke begins, the ejector 20 is moved downwards and quickly comes into contact with the upper end of the capillary 21, which will be dislodged from the tip 16.In this regard, it was noted that at this stage, piston 23 was released from the clamping system in a known manner, which will not be described here.

[0047] While the lower ejection end 60 of the ejector 20 presses on the upper end of the capillary 21, the ejector in its downward movement carries with it the locking member 64, in the form of a boss, pin, or any other raised shape capable of forming the desired radial stop.

[0048] This results in a downward displacement of the locking member 64 along the cam surface 62, allowing the lever 54 to pivot radially outwards due to its inclined plane shape. The pivoting of the lever 54 results from a radially inward pivoting of the moving portion 44, itself produced by the bearing of the capillary 21 on the portion of the bead 38 on the surface of the moving portion 44. Such a situation, permitted by the elastic deformation of the flexible linkage 52 and by the unlocking of the lever 54, is shown in the diagrams. figures 5 And 6 showing the assembly at an intermediate stage during the ejection stroke, a stage at which the mobile organ 44, constrained radially inwards, adopts a retracted position for the release of the capillary 21.

[0049] There figure 7 This represents the situation at the end of the ejection stroke, when the lower ejection end 60 of the ejector, in its lowest ejection position, has sufficiently moved the capillary 21 away so that the latter is no longer in contact with the outer surface 36 of the nozzle 16. At this stage, the movable retaining portion 44 has returned to its upright position because it is no longer constrained by the capillary 21, and under the effect of the elastic restoring force produced by the flexible zones 52 of the linkage. When the ejector 20 is released by the operator and returns under the effect of a spring to its highest rest position, the locking member 64 comes into contact with the inclined cam surface 62 of the lever, leading to the locking of the latter as on the figure 2 .

[0050] For guidance, it is noted that the initial operation of attaching the capillary 21 to the tip 16 is carried out in the classic and conventional manner, by force, by moving the pipette vertically downwards. The capillary 21 is then gripped by a slight elastic deformation of the movable retaining portion 44, until the desired contact is achieved between the rim 38 of the tip and the projection 40 of the capillary. During this gripping operation of the capillary 21, the lever 54 remains stationary in its locked position.

[0051] There figure 8represents a second preferred embodiment of the invention, in which the flexible zones 52 are replaced by a pivot or ball joint 66, here taking the form of two half-joints ensuring the connection between the two intermediate ring sectors 50a, 50b. The pivot joint 66, whose axis passes through the two half-joints, is made in a conventional manner, for example, using a shaft, a clevis, etc. The joint 66 can be equipped with elastic return means forcing the movable retention portion 44 towards its active position for retaining the capillary. Alternatively, the position of the movable retention portion 44 can be dictated by the relative position of the locking member 64 of the ejector in an inclined groove 62' formed on the lever 54.

[0052] During the ejection stroke, the locking member 64 in the form of a pin or roller, by moving in the groove 62', causes the lever 54 to tilt radially outwards, leading to a tilting of the mobile portion 44 radially inwards from its active position of retaining the capillary 21, to its retracted position of releasing the capillary.

[0053] Of course, various modifications can be made by a person skilled in the art to the invention just described, solely by way of non-limiting examples, and the scope of which is defined by the appended claims. In particular, the preferred embodiments described above correspond to the implementation of the invention on a manual, single-channel pipette, but all the lessons learned can be applied to other types of pipettes, motorized and / or multi-channel, or even to automated systems.

Claims

1. Positive displacement device assembly (30), the assembly comprising: - a tip (16) intended to support a capillary (21) of a plunger-capillary system (18), the tip being hollow, centred on a longitudinal central axis (32) of the tip, and including an outer surface (36) provided with an axial retention member (38) of the capillary, - an ejector (20) intended to eject the plunger-capillary system (18), the assembly being designed so as to enable an axial ejection travel of the ejector (20) relative to the tip (16), between a top resting end position and a bottom ejection end position, the ejector (20) comprising an ejection end (60) intended to be in axial contact with a capillary end (21) during the ejection travel, the tip (16) including a body (42) as well as a movable capillary retention portion (44) connected to the body (42) by a link (52, 52, 66), the movable retention portion (44) including on its outer surface at least a part of said axial retention member (38) of the capillary, characterised in that the tip also includes a lever (54) rigidly connected to the movable retention part (44), such that a tilting of the movable part (44) radially inwards, via the link (52, 52, 66) and relative to the tip body (42), actuates a tilting of the lever (54) radially outwards, the ejector (20) being equipped with a locking member (64) cooperating with the lever (54) such that: - in the top resting end position of the ejector (20), the locking member (64) occupies a locking position wherein it holds the movable portion (44) of the tip in an active holding position of the capillary, by preventing the lever (54) from tilting radially outwards; and - during the ejection travel of the ejector (20), the locking member (64): - allows the tilting of the lever (54) radially outwards, resulting from a tilting of the movable portion (44) radially inwards from its active holding position of the capillary, to a retracted release position of the capillary, or - actuates the tilting of the lever (54) radially outwards, resulting in a tilting of the movable portion (44) radially inwards from its active holding position of the capillary, to its retracted release position of the capillary.

2. Assembly according to claim 1, characterised in that, in the tip (16), the link (52, 52) between the movable retention portion (44) of the capillary and the tip body (42) is a flexible, elastically deformable link.

3. Assembly according to claim 2, characterised in that the tip (16) includes an intermediate ring (50) centred on its longitudinal central axis (32), and in that the flexible link is produced by two flexible zones (52, 52) of reduced thickness, between which a first angular ring sector (50a) as well as a second angular ring sector (50b) are delimited, the first angular sector (50a) being rigidly connected to the movable retention portion (44) of the capillary and the lever (54) while being arranged between the two, whereas the second angular sector (50b) is rigidly connected to the tip body (42).

4. Assembly according to claim 3, characterised in that the two flexible zones (52, 52) of reduced thickness are diametrically opposed.

5. Assembly according to claim 3 or 4, characterised in that the tip (16) also includes a fastening plate (56), rigidly connected to the second angular ring sector (50b).

6. Assembly according to any one of claims 2 to 5, characterised in that the tip (16) is made of one piece.

7. Assembly according to any one of claims 2 to 6, characterised in that the locking member (64) provided on the ejector (20) is embodied by a radial stop member, intended to cooperate with an inclined plane (62) of the tip lever (54).

8. Assembly according to claim 1, characterised in that, in the tip (16), the link between the movable capillary retention portion (44) and the tip body (42) is a pivot link (66) or a ball joint link.

9. Assembly according to any one of the preceding claims, characterised in that the movable capillary retention portion (44) has a general half-cylinder shape.

10. Assembly according to any one of the preceding claims, characterised in that another part of said axial retention member (38) of the capillary is provided on the outer surface of the tip body (42).

11. Assembly according to any one of the preceding claims, characterised in that the axial retention member (38) of the capillary is embodied using at least one annular bead on the outer surface (36) of the tip (16).

12. Assembly according to any one of the preceding claims, characterised in that the movable capillary retention portion (44) and the tip lever (54) are made of one piece.

13. Positive displacement sampling device (1) comprising at least one assembly (30) according to any one of the preceding claims.

14. Device according to claim 13, characterised in that it is a single-channel or multichannel, manual or motorised, positive displacement sampling pipette.

15. Device according to claim 13, characterised in that it is a single-channel or multichannel, manual or motorised, positive displacement sampling programmable controller.

Images