EP0032098B1 - Device for withdrawing and distributing regulated quantities of liquid, provided with a numerical display - Google Patents

Abstract

A device for sampling and dispensing adjustable volumes of liquid samples, with numerical display, is provided with a compact adjusting and display mechanism which comprises: an externally threaded sleeve which screw threadedly engages with the device housing; a prismatic control rod whose profile ensures that it rotates with the sleeve; a bush equipped, removably, with a means of causing it to rotate with the control rod; and a plurality of volume-indicator drums mounted around said bush. The sleeve serves as an adjustable end stop for a reciprocable piston actuated by the control rod.

Description

The present invention relates to a device for collecting and distributing adjustable volumes of liquid samples, with digital display.

In general, the invention therefore applies equally well to micro-pipettes equipped at their lower end with sampling cones or to displacement pipettes; positive, than to all other sampling and distribution devices such as dilutors for example.

The devices of this kind of the prior art have the drawback of comprising boxes that are too long. This excessive axial dimension of the boxes was made necessary by the very design of the adjustment and display mechanisms in accordance with the prior art, for example illustrated by French patent application FR-A-2 203 680. It should be noted that such a drawback becomes particularly troublesome in the case of handling so-called "positive displacement" pipettes, ie comprising in addition at their lower part a calibrated capillary tube of a certain length in which a piston moves in leaktight manner.

In general, it is clear that it would be easier to be able to have such dispensing and withdrawal devices having a shorter length. This makes it possible, either to better handle them in the laboratory, or even to accommodate them more easily in more sophisticated equipment, such as automatic dilutors.

The present invention therefore aims to completely modify the design of such adjustment and display mechanisms, so as to be able to limit their axial size.

• - un fourreau fileté extérieurement qui est apte à coopérer par vissage avec un filetage intérieur du boîtier, et dont l'extrémité inférieure constitue la butée réglable de limitation de course du piston;
• -une tige prismatique de commande qui traverse ledit fourreau et dont le profil assure la solidarisation en rotation avec le fourreau tout en autorisant un coulissement relatif de ladite tige par rapport audit fourreau;
• - un manchon monté libre en rotation dans la partie supérieure du boîtier, coaxialement au fourreau, et équipé de façon amovible d'un moyen de solidarisation en rotation avec la tige de commande le diametre de l'orifice interieur de ce manchon etant dimensionné de manière à permettre une pénétration du fourreau dans le manchon;
• - une pluralité de tambours indicateurs de volumes montés autour dudit manchon de façon que le tambour des unités soit solidaire en rotation avec le manchon, les autres tambours libres en rotation étant équipés de moyens d'entraînement aptes à commander le mouvement relatif des tambours en dépendance du mouvement du manchon, du fourreau et de la tige de commande, tous rendus solidaires en rotation.

According to the present invention, such an adjustment and display mechanism comprises:

• - an externally threaded sleeve which is able to cooperate by screwing with an internal thread of the housing, and the lower end of which constitutes the adjustable stop for limiting the stroke of the piston;
• a prismatic control rod which crosses said sheath and the profile of which secures in rotation with the sheath while allowing relative sliding of said rod relative to said sheath;
• a sleeve mounted freely in rotation in the upper part of the housing, coaxially with the sheath, and removably equipped with a means for securing in rotation with the control rod the diameter of the interior orifice of this sleeve being dimensioned so to allow penetration of the sheath into the sleeve;
• - A plurality of volume indicator drums mounted around said sleeve so that the units drum is integral in rotation with the sleeve, the other free rotating drums being equipped with drive means capable of controlling the relative movement of the drums in dependence the movement of the sleeve, of the sheath and of the control rod, all made integral in rotation.

According to another characteristic of the present invention, the sheath is able to penetrate substantially completely into the housing.

According to another characteristic of the present invention, the diameter of the internal opening of the sleeve is dimensioned so as to allow the penetration of the sheath into the sleeve.

• - la figure 1 représente une vue en coupe du dispositif de prélèvement et de distribution de volumes réglables d'échantillons liquides équipant, selon l'invention, un type particulier de pipettes, et
• - la figure 2 représente, à plus grande échelle, une vue en coupe du détail du mécanisme de réglage et d'affichage conforme à la présente invention.

Other characteristics and advantages of the present invention will appear on reading the detailed description given below with reference to the accompanying drawings in which:

• FIG. 1 represents a sectional view of the device for sampling and distributing adjustable volumes of liquid samples fitted, according to the invention, to a particular type of pipettes, and
• - Figure 2 shows, on a larger scale, a sectional view of the detail of the adjustment and display mechanism according to the present invention.

The pipette shown by way of nonlimiting example in FIG. 1 is of the so-called "positive displacement" type. Such a pipette conventionally comprises an upper housing 10 integral with a substantially tubular lower body 12 fitted at its lower end, in a removable manner, with a calibrated capillary tube 24 in which a piston 14 controlled in its movement moves in sealed manner. displacement by a control rod 20. In such devices the capillary tube 24 is preferably constituted by a glass tube calibrated in diameter but not in length. The piston 14 has at least one sealing zone. This piston can for example advantageously be produced in the form of a stainless steel wire having, in the case of rods of small diameters, a coating for example of Teflon. For wires of larger diameter, for example, use will be made of placing, at the lower end of the piston, a drop of teflon coming into intimate contact with the inner surface of the capillary tube 24. The length of such a piston 14 is not tolerated. Note however that the length of the latter must be greater than the length of the capillary tube 24, this being necessary to allow both its operation and the zero adjustment of the pipette. The constructive details of such a positive displacement pipette are for example described in more detail in the applicant's French patent application. FR.A. 2445672.

In the embodiment illustrated in the accompanying drawings, the stop for limiting the upward stroke of the piston is none other than the stop for limiting the stroke of the pinching member of the piston 14. This upper stop is of course adjustable in vertical position, so that the useful stroke of the sampling and distribution piston can be modified by adjusting the position of this upper stop. The lower stroke limit stop, however, remains fixed.

It is perfectly clear that the particular mechanism for adjusting and displaying the volumes, which is the subject of the present invention, is not to be limited to the specific case of a pipette with positive displacement. On the contrary, the present invention applies quite generally to a mechanism for adjusting the adjustable position of a stroke limitation stop belonging to any type of withdrawal and distribution device.

Such devices usually include an upper housing 10 secured to a substantially cylindrical lower body 12 in which a piston 14 which alternately moves is elastically urged to come into contact with an adjustable upper stop for limiting the stroke of the piston. In the particular embodiment illustrated, it is the clamping member 16 which is resiliently urged upwards thanks to the spring 18, and which is controlled in its movement simultaneously with the piston 14 by a control rod 20 passing through the housing 10. The upper end of the rod 20 is provided with a push button 22. The adjustment and display mechanism proper comprises a sleeve 26 threaded over its entire outer part, which thus enables it to cooperate by screwing with a corresponding thread made directly on the inner wall of the housing 10. In the particular embodiment shown, it is the narrowed zone 28 of the housing or else an insert or nut made integral with said housing, which will ensure cooperation by screwing. In this particular case, it will be observed that it is the free lower surface of the lower end of the threaded sleeve 26 which constitutes the adjustable stop for limiting the stroke of the sampling and distribution piston 14.

According to the present invention, the sleeve 26 is able to penetrate, substantially completely, in the cavity 30 of the housing 10. It will be observed that, in the embodiment described, the lower part of the sleeve 26 constituting the variable stop in the present position a radial peripheral projection 32 which is intended to limit the screwing depth of the sleeve 26 inside the cavity 30 of the housing 10. In the accompanying drawings, the sleeve 26 is shown in a position close to its upper limit position.

The mechanism according to the invention further comprises a prismatic control rod 20 which passes entirely through the sheath 26 and whose particular profile ensures the rotational attachment of the rod 20 with the sheath 26 while, however, allowing free relative winding of the rod 20 with respect to the sleeve 26. In the particular embodiment shown, the control rod 20 has a hexagonal section, and the threaded sleeve 26 has a through quality of homologous section. It is perfectly clear that the particular section of the control rod 20 can affect any other rectilinear or curvilinear polygonal shape or other more irregular shapes. The important characteristic of the rod-sleeve assembly is the close cooperation between these two members, so that a rotation of the control rod 20 always causes rotation of the sleeve 26 while allowing their relative free sliding.

The mechanism according to the invention further comprises a sleeve 34 which is mounted to rotate freely in the upper part of the housing 10, coaxial with the sleeve 26 and the control rod 20. It will now be noted that, during the mounting of the pipette, after having screwed the sheath 26 inside the cavity 30 of the housing 10, the sleeve 34 is placed in the upper part of the housing 10 and, at this time, the sleeve 34 remains completely independent of any rotation rod 20 and / or sleeve 26.

According to an important characteristic of the present invention, it should be noted that the diameter 36 of the internal orifice of the sleeve 34 must be dimensioned so as to allow penetration of the sheath 26 inside said sleeve 34. Such a characteristic precisely allows reduce the length of the cavity 30 of the housing 10 intended to receive the entire adjustment and display mechanism while allowing a large useful adjustment stroke. The sleeve 34 is furthermore removably fitted with a means for securing in rotation with the control rod 20. In the particular embodiment illustrated, this securing means consists of a part of revolution 38 having an orifice interior of formed homologous to the exterior profile of the control rod 20, so as to be able to rotate with the latter. In addition, the lower end of the joining piece 38 ends in a conical part 40 intended to allow it to be wedged in the upper part of the sleeve 34. Such a coincidence therefore allows the sleeve 34 and the control rod to be joined in rotation. 20. This particular provision will make it possible in particular to adjust the pipette to zero, for example during assembly at the factory.

The orifice in the upper part of the housing 10 is advantageously closed by a snap-on cover 42 simultaneously ensuring that the sleeve 34 and the various volume indicator drums described in more detail are held in place below. The sleeve 34 shown in the accompanying drawings has at its lower part a radial projection 44 intended to cooperate with a homologous recess 46 formed on the inner wall of the housing 10. When mounting the pipette, it will be noted that it suffices to set in place places the sleeve 34, the correct positioning of which is facilitated by the presence of this protrusion 44 which cooperates with the step 46. To calibrate the pipette in the factory during assembly, or possibly during a revision, it is then advantageously possible to operate the next way. We proceed to the complete screwing down of the sleeve 26, until we reach the useful end of the piston 14. At this moment, we will observe that the sleeve 34 remains always free in rotation relative to the rod. control 20 and relative to the sleeve 26. This allows the volume indicator drums to be placed in their position for displaying zero. Then, after having snapped on the cover 42, the fastening piece 38 is introduced, the conical lower part 40 of which comes to coincide the upper part of the sleeve 34 against a flange 48 formed on the lower part of the cover 42 of the pipette. Zero adjustment is thus carried out very easily, while remaining very precise. It will be noted precisely that the joining piece 38 has, in the vicinity of its upper part, a crown 50 provided with a peripheral groove intended to receive a friction ring 52 which, by cooperation with the homologous part of the cover 42, ensures the immobilization of the adjustment mechanism in the position chosen by the user. In practice, for example, it is possible to use a four-lobe seal to provide this locking function. Advantageously, such a braking ring 52 will be made of an elastically deformable flexible material, resistant to wear and tearing. For this purpose, use will be made, for example, of a braking ring made of a material chosen from fluorocarbon resins, polychloroprene and preferably polyurethanes.

The upper part of the attachment piece 38 comprises a sort of crown provided with a peripheral groove 54, a recess or even a projection intended to materialize a gripping area, to allow the extraction of said attachment piece 38 outside the sleeve 34. Since this dismantling operation of the adjustment and display mechanism of the pipette should in principle only be carried out in the factory, these gripping zones will be very difficult, if not at all, accessible from outside the housing 10, and will preferably require the use of a special shaped key intended to allow the extraction of this part only by qualified personnel.

The mechanism for ensuring the display of the sample volume chosen by the operator also includes a plurality of volume indicator drums. These volume indicator drums, for example the drum of the units 56, the tens drum 58 and the hundreds drum 60, are mounted around said sleeve 34 so as to stack them on top of each other. It will be noted that the radial projection 44 previously described also makes it possible to avoid sliding downwards and placing the first drum 56 indicating the units in exact position. It should be noted that this first drum of the units must be integral in rotation with the sleeve 34. This attachment can be obtained, for example by wedging, by gluing or by any other suitable means. On the other hand, the other drums (tens 58 and hundreds 60) remain completely free to rotate around the sleeve 34. These drums are however obviously coupled with drive means capable of controlling their relative displacement in dependence on the movement of the sleeve 34 , the movement of the sleeve 26 and the movement of the control rod 20, which are all integral in rotation as seen previously when the pipette is fully assembled.

In the particular embodiment illustrated, the drums respectively indicate the volume settings in units, tens and hundreds of microliters. It is perfectly possible to provide more or less drums, graduated in any desired unit. The movement of the drums relative to each other is carried out in a conventional manner. For a complete rotation of the drum 56 of the units, only a pair of teeth drives a rock 62 mounted on a shaft 64, which penetrates into the snap-on cover 42. Rock 62 drives continuous gears on the tens drum 58 to move it d 'a tenth of a turn. Similarly, a complete rotation of the tens drum 58 causes a unitary movement of the hundreds drum 60 by the play of a simple pair of gear teeth, an additional rock 66 and a continuous gear on the hundreds drum. 60.

It will also be noted that the casing 10 of the pipette conventionally comprises a transparent window 68 allowing the reading of the indicator drums.

According to another characteristic of the present invention, the push button 22 is produced in two independent parts. Only the lower part 70 drives the control rod 20 in rotation. This solidarity in rotation of the lower part 70 of the push button 22 can be obtained by any suitable means, for example by giving the orifice passing through this lower part 70 of the button 22 a shape homologous to the external profile of the control rod 20. On the other hand, the upper part 72 of the push button remains completely free to rotate both relative to the control rod 20 relative to the lower part 70 of the push button 22. Such an arrangement has the advantage of avoiding any risk of the pipette being adjusted during use of the pipette. The operator thus exerts pressure on the upper part 72 and only on this upper part of the button 22 using his thumb. With a unitary button, it could indeed occur, during a push on the rod 20 mainly during the ejection stroke, that the thumb impresses on the upper part of the button a certain force tending to slightly rotate the latter . With the particular conformation in two independent parts of the push button, there is therefore no longer any risk of adjustment during use. This can be decisive in the case of series of measurements, where the operator seeks to take successively several strictly identical samples.

Of course, the present invention cannot be limited to the particular embodiments described, but it is perfectly possible without departing from the scope of the present invention to imagine a certain number of variants of detail.

Claims (10)

1. A device for removing and distributing adjustable volumes of liquid samples of the type comprising an upper casing (10) integral with a lower substantially cylindrical body (12), in which a piston (14) is alternately displaced which is resiliently urged to come into contact with an adjustable stop for restricting the path of the piston and which is controlled in its displacement by a control rod (20) passing through the casing and the top end of which is provided with a push button (22), characterised by a mechanism for adjusting the position of said stop and for displaying the volume of the corresponding sample, said mechanism comprising in combination:

- an externally threaded cover (26) which is capable of cooperating, by screwing, with an inside thread of the casing (10), and the lower end of which forms said adjustable stop;

- a prismatic control rod (20) which passes through said cover, and the profile of which ensures the integration in rotation with the cover while allowing a relative sliding movement of said rod with respect to the cover;

- a sleeve (34) which is mounted free in rotation in the upper part of the casing coaxially to the cover and is equipped in a removable manner with a means for integration in rotation with the control rod, the diameter of the inside orifice of this sleeve being dimensioned so that it allows the cover to penetrate the sleeve,

- plurality of volume indicating barrels (56, 58, 60) which are mounted around said sleeve so that the barrel of the ones (56) is integral in rotation with the sleeve (34), the other barrels free in rotation being provided with driving means (62, 66) which are capable of controlling. the relative movement of the barrels depending on the movement of the sleeve, of the cover and of the control rod which are integrated in rotation.

2. A device according to claim 1, characterised in that the cover is capable of substantially completely penetrating the casing.

3. A device according to one of claims 1 or 2, characterised in that the cover has, preferably in the vicinity of its lower end, a radial projection limiting the depth to which the cover is screwed into said casing.

4. A device according to one of claims 1 to 3, characterised in that the orifice of the upper part of the casing is sealed by a lid ensuring that the sleeve and the volume indicating barrels are maintained in position.

5. A device according to one of claims 1 to 4, characterised in that the means for integrating in rotation the sleeve with the control rod comprise a part which has an inside orifice of a homologous shape to the external profile of the control rod and the lower end of which is terminated by a conical part which is to ensure a wedging in the top part of the sleeve.

6. A device according to claim 5, characterised in that said integration part has at its top part a crown provided with an external groove which is to receive a friction ring cooperating with the homologous part of the lid.

7. A device according to claim 6, characterised in that said crown has in the vicinity of its top part gripping means to allow the integration part to be extracted from the sleeve.

8. A device according to one of claims 1 to 7, characterised in that the length of the cover is calculated so that it penetrates the sleeve to as great a depth as possible.

9. A device according to one of claims 1 to 8, characterised in that the lower part of the sleeve has a radial projection which is to cooperate with a homologous unhooking element made in the inside wall of the casing.

10. A device according to one of claims 1 to 9, characterised in that the push button of the prismatic control rod is made in two substantially equal parts, the lower part being integral in rotation with said control rod and the upper part remaining free in rotation with respect to said lower part and with respect to said control rod.

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