Centrifuging device for laboratory analyzer

A device for centrifuging various samples of a product or a mixture of products which are chemical or biological, the device including a vessel which is open at the top and contains a vertical central shaft driven in rotation by a rotary driving means, a horizontal plate mounted interlocked in rotation on the central shaft and provided on its surface with a plurality of through orifices for the mounting of tubes which are each intended to contain a volume of a sample to be centrifuged, these through orifices having a substantially elongate shape with front and rear walls inclined at an acute angle of less than 90 degrees relative to the horizontal, and means for indexing the position of the plate each time the plate stops, in order to position through orifices of the tubes at predetermined sites.

BACKGROUND OF THE INVENTION

The present invention relates to a device for centrifuging various samples of a product or a mixture of products which are chemical or biological.

In the field of chemistry or biochemistry, the centrifuging of samples is commonly employed to separate different phases (organic, aqueous) in order to extract and purify particular molecules.

In biology, the centrifuging of samples is often used to separate solid particles (cells or bacteria) held in suspension or even in emulsion in the liquid phase.

During the last thirty years, in the various fields of research in chemistry, in biochemistry or in biology, the trend has been to automate the majority of experimental protocols in order to meet criteria of production, speed, quantity and reliability.

This automation of the protocols is carried out using laboratory robots or analyzers mounted in proximity to the working plane on which said protocols are carried out.

These laboratory analyzers or robots generally comprise three mutually perpendicular axes X, Y and Z for the spatial positioning of a head provided with a liquid suction/dispensing system or provided with a gripping system, or alternatively equipped with these two systems.

The laboratory robot or analyzer can transfer reagents and/or biological solutions from one receptacle to the other, which is positioned at various sites on the working plane whose useful area is on average less than 0.3 m2, with a view to conducting reactions, for example enzymatic or colorimetric reactions.

Automation of the experimental protocols requires the placement of all the elements needed for these protocols, for example the test tubes or other supports, the containers of reagents or samples to be processed, the various accessories, such as water-bath heating systems, cooling apparatus or the like, on the working-plane useful surface which is swept by the head of the laboratory analyzer or robot.

The centrifuging step does not currently form part of the steps of the automated experimental protocols, because the available centrifuging devices are not designed to cooperate with a laboratory robot or analyzer as mentioned above.

This is due to the fact that the currently known centrifuging device has a motor for driving a rotor in rotation, which always stops randomly relative to a given point. Since the laboratory robot or analyzer which is used does not have an integrated visualization system, such a robot or analyzer could not find the samples at a given site after the centrifuging step.

Furthermore, in the known centrifuging devices, the tubes intended to contain the samples to be centrifuged are oriented in a fixed position at a certain inclination relative to the axis of the rotor, so that when the rotor is rotating the samples do not escape from the tubes and the centrifuging concentrates are positioned toward the front of the tubes.

However, as mentioned above, a laboratory robot or analyzer works along three perpendicular axes X, Y, Z and cannot operate along an inclined axis.

It is hence incapable of sucking a part of the centrifuged sample placed in the bottom of the tubes, which are positioned so as to be inclined in the centrifuging rotor.

Lastly, the currently marketed centrifuging devices have external dimensions, and in particular an external height, which prevents them from being put on the working plane of laboratory robots or analyzers.

Consequently, because of the difficulties involved with the centrifuging step in an automatic sequence of steps according to a specific experimental protocol, new separation techniques have recently been developed.

For example, in the field of biotechnology, separation columns based on molecular differentiation as a function of size have been developed.

Other techniques for the replacement of centrifuging consist in using a principle of affinity-binding of molecules on magnetic beads.

These new steps, corresponding to new steps for the replacement of centrifuging, nevertheless have certain problems when they are integrated in an automated experimental protocol.

In the case of separation columns, in particular, it is generally difficult to control the flow rate of the various columns which are placed on a laboratory robot or analyzer.

As regards the use of magnetic beads, these represent a cost which is still significant, and this rules out its integration in large-scale processing of samples.

SUMMARY OF THE INVENTION

In order to overcome the various aforementioned drawbacks of the prior art, the present invention provides a novel device for centrifuging various samples of a product or a mixture of products which are chemical or biological, which is intended to be positioned on a horizontal working plane whose available area is less than or equal to 0.4 m2, in order to cooperate with a laboratory analyzer mounted in proximity to the working plane for automatically performing biological or chemical reactions according to a specific protocol, the external useful height of which centrifuging device is less than or equal to about 20 cm.

Advantageously, this centrifuging device comprises in a casing:a vessel which is open at the top and contains a vertical central shaft driven in rotation by a rotary driving means,a horizontal plate, mounted interlocked in rotation on the central shaft and provided on its surface with a plurality of through orifices for the vertical mounting of tubes which are each intended to contain a volume of a sample to be centrifuged, these mounting orifices having a substantially elongate shape with front and rear walls inclined at an acute angle of less than 90 degrees relative to the horizontal, andmeans for indexing the position of the plate each time the plate stops, in order to position said mounting orifices of the tubes at predetermined sites.

The centrifuging device according to the invention hence makes it possible, in a small volume matched to the available area of a laboratory working plane on which a laboratory analyzer is mounted, to position a large number (greater than or equal to about 48) of tubes containing samples in a vertical position when stopped, and to centrifuge these tubes in a suitable inclined position so that the samples contained in the tubes stay in the tubes, with centrifuging concentrates positioned correctly in the bottom of the tubes, and while preventing the tubes located on the outer edge of the plate from bending so as to deform plastically under the effect of the acceleration which they experience.

When the centrifuging cycle is completed, the tubes positioned in their mounting orifices of the plate of the device according to the invention return to the vertical position under the effect of their own weight, and the indexing means of said device position the plate so that the tubes are at a specific position, which allows a laboratory analyzer or robot head to take the full amount of the centrifuged samples from each tube.

According to an advantageous variant of the centrifuging device according to the invention, it comprises in a casing:a vessel which is open at the top and contains a vertical central shaft driven in rotation by a rotary driving means,a horizontal plate, mounted interlocked in rotation on the central shaft and provided with arrangements for the parallel mounting, in proximity to each other, of two swing trays for supporting two sample-receptacle holders which can pivot freely about a horizontal axis in order to assume a horizontally inclined position during the rotation of the plate, andmeans for indexing the position of the plate each time the plate stops, in order to position said swing trays at predetermined sites.

These receptacle holders are preferably microplates.

Advantageously, in this case, the plate has two diametrically opposite notches in which the swing trays are mounted so as to pivot in such a way that the pivoting axis of said swing trays is offset toward the center of the plate relative to the vertical axis passing through the center of gravity of each swing tray.

This makes it possible, when the plate is stopped after a centrifuging cycle, for the swing trays to return automatically under the effect of their own weight against a stop which secures them in a vertical position of stable equilibrium.

According to another embodiment of the centrifuging device in accordance with the invention, the horizontal plate may be provided with said orifices for mounting the tubes and have arrangements for the parallel mounting of said pivoting swing trays which support the microplates.

Furthermore, according to another embodiment, the centrifuging device in accordance with the invention may have two identical vessels containing two identical plates which are linked in rotation and are driven simultaneously by a rotary driving means.

According to other characteristics of the device in accordance with the invention:the rear and front walls of said mounting orifices of the plate are inclined by an angle of less than or equal to 60 degrees relative to the horizontal,the indexing means of each plate comprise a disk which is mounted below each plate so as to be interlocked in rotation with the vertical drive shaft and is provided with a recess provided in its outer peripheral edge, a horizontal finger which is held in contact with the disk by an elastic means when the plate is stopped and when it is being indexed and is separated from the disk by an actuator when the plate is rotating in the centrifuging phase, and means for pivoting the plate stepwise in the indexing phase until said finger cooperates with the recess of said disk,it has a lid which closes the vessel or vessels and is mounted so as to pivot on the casing,it has a lid which closes the vessel(s) and is mounted so as to slide on the casing, said indexing means comprising a rack of specific length which is provided on the inner face of the closure lid and is intended to cooperate with a toothed-sector wheel carried by the drive shaft of a plate, when opening the vessel(s) by sliding the lid,the vessel in the shape of a cylinder of revolution has a diameter of the order of 300 mm, a height of the order of 85 mm, for a horizontal plate with a diameter of the order of 270 mm, the casing enclosing the vessel having an external width and length of the order of 320 mm and a height of the order of 120 mm,the size of the mounting orifices of each plate is designed to hold tubes with a volume equal to 2 ml or 5 ml,the maximum rotational speed of the plate, in the case when it holds tubes with a volume equal to 2 ml, is of the order of 13,000 revolutions/minute and, in the case when it holds tubes with a volume equal to about 5 ml, is of the order of 4500 revolutions/minute with swing trays, and without any swing tray the maximum rotational speed of the plate with tubes having a volume of 5 ml is of the order of 5000 revolutions/minute.

The description which follows with reference to the appended drawings, which are given by way of nonlimiting examples, will clearly show what the invention consists of and how it can be implemented.

DETAILED DESCRIPTION

Referring toFIGS. 1 and 2, a working plane1has been represented, on which a laboratory robot or analyzer2works in order automatically to carry out experimental protocols in the field of chemistry, biochemistry or biology.

To that end, in the known way, the robot2is mounted in proximity to the working plane1and has a head2awhich can be moved vertically and horizontally along mutually perpendicular axes X, Y and Z so as to reach various sites on the working plane, where tubes106intended to contain various samples of a product or a mixture of products which are chemical or biological, reagent receptacles4,5and accessories6such as a water bath, cooling apparatus or the like are arranged.

The maximum height available between the head2aof the robot2and the working plane1is of the order of 20 cm, and the useful area1of the working plane1swept by the robot is less than or equal to 0.4 m.

In this aforementioned available volume, taking account of the aforementioned elements which are already positioned on the working plane, a centrifuging device100is positioned with which the robot2cooperates in order automatically to carry out a step of centrifuging samples for the implementation of chemical or biological reactions according to specific automated experimental protocols.

Referring first toFIGS. 3,4and6, this centrifuging device100has, in a casing101, a vessel102which is open at the top and contains a vertical central shaft103driven in rotation about its axis V by means of a rotary driving means, here an electric or pneumatic motor (not shown). A horizontal plate104is mounted on this vertical rotary drive shaft103so that it is interlocked in rotation with said shaft103.

According to the embodiment represented in these figures, the plate104is of circular overall shape and has two notches104a,104bwhich each have a vertical back wall, the two vertical back walls being parallel and arranged very close to the rotary drive shaft103, and two opposite side walls which extend radially as far as the outer peripheral edge104cof the plate104, each side wall having a shoulder104a,104′bforming a stop projecting outwards.

The majority of the surface of the horizontal plate104is provided with through orifices105, having vertical axes, for the mounting in a vertical position of tubes106which are intended to contain volumes of samples to be centrifuged. To that end, the tubes106, which are made conventionally of a plastic material such as polyethylene, have a holding collar106aon their outer surface, in proximity to their upper opening, so that when the plate104is in a stopped position, said tubes106engaged in the through orifices105are positioned vertically while resting on the plate104via the holding collar106a.

The mounting orifices105are arranged along arcs of circles which are concentric with the rotary drive shaft103, distributed between the outer peripheral edge104cof the plate104and its central region.

Furthermore, according to the embodiment represented inFIGS. 3,4and6, the plate104carries, in each of its notches104a,104b, a swing tray107,108which supports a holder for receptacles of products to be centrifuged, here a microplate of 96 wells107a,108a. Each swing tray107,108comprises a base supporting a microplate and two parallel uprights107b,108bprovided with openings107c,108cfor mounting it on the plate104. The bases supporting the swing trays107,108comprise tabs107d,108dfor securing and locking the microplates on said swing trays. Each swing tray107,108is mounted so as to pivot freely on horizontal bearings carried by the side walls of each notch104a,104bso that it can change from a vertical equilibrium position when the plate104is stopped, with its support base horizontal (see FIG.3), for loading the microplates and injecting and withdrawing samples, to a horizontal equilibrium position when the plate is rotating, with its support base vertical (see FIG.4).

The dimensions of the notches104a,104bof the plate104are such that the swing trays107,108are as close as possible to each other, here the minimum distance between said swing trays when stopped is of the order of 70 mm.

Advantageously, the swing trays107,108are pivotally mounted in such a way that, when the plate is stopped, each swing tray returns under the effect of its own weight into a vertical stable position with its uprights107b,108bbearing against said stops104a,104bof the notches104a,104bof the plate104. To that end, the horizontal pivoting axis of each swing tray is offset toward the center of the plate104relative to the vertical axis passing through the center of gravity of said swing tray.

The swing trays107,108are, for example, made of a metallic material, preferably high-strength inoxe®, so that they can withstand, without plastically deforming, the centrifugal force exerted on them when the plate rotates, this being a force which can reach a very high value in excess of one tonne. As a variant, the swing trays may also be made of a composite material such as carbon.

The plate104is made of a metallic material, preferably a low-density material, here a high-strength aluminum alloy protected by chemical nickel plating in order to comply with sanitary standards.

According to the example represented inFIGS. 3,4and6, the vessel102in the shape of a cylinder of revolution about the central axis V has a diameter of the order of 300 mm, preferably 305 mm, and a height of the order of 85 mm, which gives a diameter of the order of 270 mm for the horizontal plate104. There is therefore very little space, about 15 mm, available between the outer peripheral edge104cof the plate104and the cylindrical wall of the vessel102. Furthermore, the part of the plate104provided with the mounting orifices105has a thickness of the order of 5 mm and, at the notches104a,104b, said plate104has a thickness of the order of 25 mm. The part of the casing101containing the vessel102has an external width and length of the order of 320 mm. The casing101is extended here laterally to contain the electronics used for automated control of the operation of the centrifuging device, in particular starting and stopping the rotary drive motor, and control of the closing and opening of the closure lid109of the vessel102. The casing hence has a total length of the order of 480 mm. The height of the casing101, level with the vessel102, is of the order of 120 mm, preferably of the order of 117 mm and, level with the electronics, of the order of 200 mm.

Of course, according to a variant (not shown), the control electronics part may be decoupled from the vessel part of said centrifuging device, by positioning the control electronics in a different casing which is positioned at a different site on the working plane, and the electronics may be connected to the vessel part containing the rotary drive motor by electrical connection wires. Only the part of the casing directly enclosing the vessel hence needs to be taken into consideration when evaluating the external dimensions of the centrifuging device100.

In the embodiment represented inFIGS. 3,4and6, the plate104has 48 orifices for supporting 48 tubes106.

The size of the mounting orifices105is designed to hold tubes with a volume equal to about 5 ml. The maximum rotational speed of the plate104, which carries the swing trays107,108, is of the order of 4500 revolutions/minute. This maximum rotational speed gives a centrifugal thrust, exerted on said rotating swing trays, of the order of 1.5 tonnes, which is the upper limit tolerable by the swing trays so that they do not the form plastically.

Of course, according to a variant (not shown), the turning plate may be a solid disk of constant thickness, for example of the order of 5 mm, which is provided over its entire surface with through orifices for the mounting of tubes containing the samples to be centrifuged, and which does not have arrangements for the mounting of swing trays supporting microplates. These mounting orifices which, for example, are identical to those of the version represented in the aforementioned figures will then be distributed along circles concentric with the drive shaft of the plate. In this case, the number of mounting orifices would be at least doubled and around one hundred tubes carried by the plate would be achieved. According to this variant, the maximum rotational speed of the plate is then of the order of 5000 revolutions/minute. A small number of orifices, but with larger dimensions for tubes with greater volumes, may also be envisaged.

As shown more particularly byFIG. 5, each orifice for mounting the tubes105has an elongate shape, here oblong, with parallel rear105aand front105bwalls inclined by an acute angle of less than 90 degrees relative to the horizontal. The front and the rear are defined here in terms of moving away from the axis V of rotation of the plate. More particularly, according to the typical case represented inFIG. 5, the angle of inclination relative to the horizontal of said rear and front walls of each orifice105is less than or equal to 60 degrees.

The tubes106, which are positioned vertically in said orifices when the plate is stopped, hence assume an inclined position, which is here 30 degrees relative to the vertical or 60 degrees relative to the horizontal, under the effect of the centrifugal force when the plate rotates.

At this inclination, the sample contained in each rotating tube does not overspill the tube, the centrifuging concentrate is properly positioned at the bottom of the tube, as is desirable, and above all the deformation of the tubes positioned outermost on the plate, which is due to the centrifugal force, stays below the elastic deformation limit of said tubes.

More particularly, in order to determine the inclination slope of said rear and front walls of said orifices, the following elements are taken into account.

Firstly, this angle of inclination is determined such that, for a given tube mass, the acceleration experienced by the tubes located outermost on the plate (distance R1) does not cause their permanent deformation.

In particular, for a given angle of inclination, the deformation amplitude of these tubes should be less than a limiting value above which the tube plastically deforms.

The amplitude is given by the following formula:
A=F.L3/8.E.I, whereE is the modulus of elasticity of the material used for the tube,I is the stressed cross section,F is the centrifugal force applied to the tube, andL is the distance between the center of gravity G of the tube and the point C where the tube is pivoted in the mounting orifice.

In the example represented inFIGS. 3 and 5, assuming a density equal to 1 and a sample volume of 5 ml contained in the tube, the mass to be taken into consideration is hence equal to 5 g. For a rotational speed of 4500 revolutions/minute, the acceleration experienced by said tubes located at the outside of the plate is of the order of 14,000 G, which gives a centrifugal force F equal to 17 newtons. Knowing the values of E and I for a given tube, a check was made that an angle of inclination of 30 degrees relative to the vertical gave a value of the amplitude below said limiting value (L=a sin(30) is here equal to 16 mm, a representing the distance between the pivoting point C and the center of the mounting orifice). In the illustrative embodiment represented in theFIGS. 3,4,5and6, the limiting value of the amplitude is reached for a centrifugal force of the order of 140 newtons.

A check was then made that this angle of inclination makes it possible, during the rotation of the plate, to contain all of the sample volumes in the tubes located at the outside of the plate, since they are the ones which experience the strongest acceleration. This is the case when the center of gravity G of the sample is placed precisely below the point where the tube is pivoted in the orifice.

Furthermore, the centrifuging device100represented inFIG. 3has a lid109which closes the vessel102. This lid109is here mounted so as to pivot via hinges109aon the casing101. The closure lid109has a height of about 55 mm. When it is opened, however, its dimension exceeds the height available under the head of the laboratory robot.

As shown inFIG. 2, the centrifuging device100is hence positioned on the working plane1so that only the vessel part is located in the useful surface S of the latter, which is swept by the head of the robot, and the electronics part of the casing of this centrifuging device as well as its closure lid, when opened, are located outside this useful surface S of said working plane1.

Furthermore, as shown more particularly byFIGS. 6 and 7, the centrifuging device has means120for indexing the position of the plate104, each time said plate stops, in order to position the mounting orifices of said tubes and said swing trays at the same specific sites each time. The indexing means120comprise here, on the one hand, a disk123which is mounted below the plate104so as to be interlocked with the rotary drive shaft103and is provided with a recess124provided in its outer peripheral edge125, and, on the other hand, a horizontal finger126which is actuated using an elastic means127, for example a spring and electromagnet, between a separated position, when the plate is driven in rotation during the centrifuging phase, and a position bearing against the outer peripheral edge125of the disk123, after the plate has been stopped. The horizontal finger126is held bearing against the disk123when the plate is rotated stepwise about its axis of rotation until cooperating with the recess124of the disk, where the plate is positioned in a specific way. The stepwise rotation of the plate with a view to indexing it may be carried out either by the main motor in successive pulses, or by a secondary actuator.

FIG. 8represents an alternative embodiment of the centrifuging device, according to which it has, in a casing101′, two identical vessels102,102′ of smaller volume which are each provided with a turning horizontal plate104,104′.

Each plate104,104′ is driven in rotation by means of a vertical central shaft103,103′. The vertical shafts103,103′ are linked in rotation by a notched belt system, for example, and are driven simultaneously in rotation by means of a single drive motor (not shown).

According to this variant, each plate104,104′ is provided over its entire surface with orifices105,105′ for the mounting of tubes intended to contain samples to be centrifuged.

Here, the size of the orifices105,1051is such that they hold tubes with a volume of the order of 2 ml.

The maximum rotational speed of the plates is hence of the order of 13,000 revolutions/minute.

Of course, the external dimensions of the casing101′ are similar to those of the casing101of the first embodiment described.

Lastly, the centrifuging device represented inFIG. 8has a lid109′ which closes two vessels102,102′ and is mounted so as to slide by means of a rail on the casing.

In this case, the means for indexing the position of the plates after the latter have been stopped comprises a rack121which is positioned on the inner face of the lid109′ and a toothed-sector wheel122mounted on a rotational drive shaft103of a plate.

The rack of specific length becomes active when the lid109′ is opened, whereupon it cooperates with the toothed sector122aof the wheel122, and is inactivated when the flat122bof the wheel122is parallel to it. When the lid is closed, since the indexing has already taken place, the rack will then systematically find the parallel flat122bof said wheel122, and will in this case clearly be inactive.

The present invention is in no way limited to the embodiments which have been described and represented, and the person skilled in the art will be able to add any variation to it in accordance with its spirit.

In particular, according to one variant (not shown), the plate of the centrifuging device may not have orifices and may be used only as a support for the pivotal mounting of said swing trays.