EP1171242B1 - Liquid centrifuging apparatus and use of same - Google Patents

Description

The present invention relates to a centrifuge apparatus liquid, especially blood, containing suspended particles comprising a first drive member rotatably mounted, a second drive member rotatably mounted, coaxial with the first drive member, means for training said first and said second drive member, with a rotation ratio of 2/1 between them, a member for centrifuging said liquid, provided with at least three channels connecting its center to a room separation device, means for rendering said centrifuge member integral with said first member drive, three conduits made of elastically deformable material, each having a first integral end from the central end of one of the three channels of said centrifuge member, these conduits each forming a open loop around said centrifuge member, the second end of this loop being substantially coaxial at the first and angularly fixed, a portion of each loop being kinematically integral with said second member one of said conduits being connected to a power source for said liquid to be centrifuged, both others used to recover components of different densities from centrifugation. This invention relates also to use this device.

Such centrifuge devices are well known especially in the field of blood centrifugation, since they allow the centrifuge rotor to be connected outside to supply it with liquid to be centrifuged and remove the separate components without using seal. Indeed, it is known from US 3,586,413 that if you have a flexible duct forming an open loop and whose two ends are coaxial, that one is fixed while the other rotates at 2ω speed around the axis common to these two ends and that the loop is driven at speed ω, the flexible duct rotates around its own axis at speed -ω, canceling the induced twist by the rotation of the rotor.

In the case of blood centrifugation, the separation must be changed for each donor or each different patient. Given the centrifugal forces required to obtain the desired separation of the constituents, the centrifuge rotor must be able to withstand the forces centrifugal to which it is subjected, it must be sized suitably it must be balanced to avoid unbalance and it must be fixed securely on the axle of rotation.

Different ways have been adopted to satisfy these requirements, one is to use a rotor integral with the centrifuge and drive system provide positioning means to receive one or more several centrifuge chambers. Such a solution is described for example in US 4,164,318.

Another solution described in US 4,834,890 consists to provide a rotor having an annular housing intended to receive a flexible bag serving as a separation enclosure. The placement of the bag in the annular housing is an extremely delicate operation. To give back this easier operation, we proposed in US 4,934 995 to make the rotor in two parts between which is provided the housing intended to receive the flexible bag for liquid separation.

Another system comprising a rigid rotor intended for receive a flexible bag for liquid separation a have been offered in US 4,007,871.

US 4,790,807 relates to a rigid enclosure but flexible formed by a split ring, both of which end are spread apart. To set up this speaker in the support rotor, the two ends are brought together of the split ring which is then retained in a housing of the rotor by its elasticity.

Finally, we have also proposed, in US 4,330,080 a rigid and disposable rotor in the form of a disc two parts, one comprising two annular chambers for separation of constituents of different densities and channels to bring the liquid to centrifuge and to allow the evacuation of the constituents resulting from the separation.

The drive shaft of this rotor is constituted by a tubular element allowing the passage of the liquid conduits to centrifuge and constituents from the separation. The outside of the tube has an annular surface gear intended to engage a pinion of the mechanism device drive, a first profile disc convex is placed on one side of the annular toothed surface and is intended to engage with three guide pulleys with concave profiles. A second disc, placed on the other side of this toothed annular surface is engaged with three other guide rollers. Such a drive mechanism and guiding is extremely complex. To remove the disposable rotor, you must be able to separate one of the associated rollers to each of the guide surfaces, so that these rollers must also be mounted on mobile supports which must be locked during the centrifugation process. So this is a system in which change disposable rotor is not an easy operation, neither quick to achieve.

We can therefore see that it does not exist in this domain an assembly formed by a rigid separation enclosure forming a bowl and its supply conduits and which allows a quick and easy change.

US-A-4,261,507 discloses a blood centrifuge apparatus, in which the centrifuge member is reversibly attached to the first drive member by means of a clamp and a spring.

The object of the present invention is to remedy, less in part to the disadvantages of the above-mentioned solutions.

To this end, this invention relates to an apparatus for centrifuging liquid, especially blood, of the type above, as defined by claim 1.

This invention also relates to a use of this centrifuge, as defined by claim 24.

The apparatus according to the invention is therefore of the type in which the circular centrifuge member forms a single disposable member, integral with the conduits used for feeding and the collection of liquids. The fixation of the organ circular centrifugation on its drive member is obtained by manual latching. The fixing system is not subject to centrifugal forces since it works axially. Once the attachment is obtained, there is therefore no risk of untimely separation. The dropout of the centrifuge unit requires only a simple pull axial against elastic spring pressure holding. No other mechanical element than the second coupling element is not located on the centrifuge member, so this one constitutes a simple piece and cheap to make. The simplicity and speed of centrifuge member change operations as well that the price of it therefore allow a gain substantial, on the one hand on the price of the material, on the other share on the cost of centrifugation. This economy is extremely important especially when the device according the invention is used for the collection of plasma.

la figure 1 est une vue en coupe d'une élévation de cette forme d'exécution;

la figure 2 est une vue partielle en coupe, selon la ligne II-II de la figure 1,

la figure 3 est une vue schématique de la cinématique du mécanisme d'entraínement,

la figure 4 est une vue agrandie en coupe selon la ligne IV-IV de la figure 1,

la figure 5 est une vue partielle en coupe, d'une variante de la forme d'exécution de la figure 1,

la figure 6 est une vue selon la ligne VI-VI de la figure 5;

la figure 7 est une vue semblable aux figures 1 et 5 d'une autre variante.

The invention will be better understood on reading the following description of an embodiment and a variant of the liquid centrifugation apparatus according to the present invention, illustrated schematically and by way of example by the appended drawing in which,

Figure 1 is a sectional view of an elevation of this embodiment;

FIG. 2 is a partial sectional view, along the line II-II of FIG. 1,

FIG. 3 is a schematic view of the kinematics of the drive mechanism,

FIG. 4 is an enlarged sectional view along the line IV-IV of FIG. 1,

FIG. 5 is a partial sectional view of a variant of the embodiment of FIG. 1,

Figure 6 is a view along line VI-VI of Figure 5;

Figure 7 is a view similar to Figures 1 and 5 of another variant.

The centrifuge apparatus illustrated in FIG. 1, intended in particular for plasmapheresis, comprises a rotor centrifugation or first drive member, having the shape of a disc 1 arranged at the end of a tubular body 1a, pivotally mounted in two ball bearings P1, P2. This centrifuge rotor 1 carries a centrifuge bowl 2 or disposable centrifuge member, formed itself by the union of two parts welded or glued one to the other, the lower one, formed by a disc 2a and the other upper 2b, having two cylindrical side walls and concentric, one inside 2c and the other 2d exterior between which an enclosure is formed separation ring 3 or peripheral separation chamber (Figures 1 and 2). Three channels radials 4, 5, 6, formed in the upper part 2b of the centrifuge bowl 2, connect this annular enclosure separation 3 in the center of this bowl 2. Channel 4 constitutes the blood supply channel to be centrifuged. he has a partition 7 which joins the side wall 2d of the annular separation enclosure 3, while the other wall of this feed channel 4 stops at the side wall internal 2c of this separation enclosure 3.

The partition 7 also serves to separate the channel 4 from the channel 5 intended for the recovery of blood cells, of which the other partition 8 stops at a certain distance from the 2d external side wall of the annular enclosure of separation 3. This partition 8 therefore separates channels 5 and 6 and communicates them respectively with the external party of the annular separation enclosure 3, that is to say that where the blood cells are concentrated, that of lower density where the plasma is concentrated. Of course, subsequent separation of recovered blood cells is possible to separate red blood cells, red blood cells blanks and pads. In a variant of the bowl 2, we could also consider having more than two output channels to achieve this separation.

These three channels 4, 5 and 6 lead to the center of the bowl 2 where they are connected to three conduits 4a, 5a, respectively 6a (Figure 4) which are preferably arranged parallel in the same flexible tubular element 9. The portion of this tubular element 9, adjacent to its end connected to channels 4, 5 and 6 is held in a housing tubular 10 formed coaxially with the axis of rotation of the bowl 2, on the upper part 2b thereof. The sections of the three conduits 4a, 5a, 6a are elliptical, the major axes of these ellipses being tangent to at least one circle concentric with the longitudinal axis of the tubular element 9. This orientation of the elliptical sections of the conduits 4a, 5a, 6a, facilitates the rotation of the tubular element around its longitudinal axis.

It appears from the above that the movable part called to be discarded after each use does not consist that of three parts, the bowl 2 formed of two parts 2a, 2b welded or glued to each other and the tubular element 9. In addition, this set does not require any seal sealing. This set is removably connected to the centrifuge rotor 1 as described below.

The bottom of the disc forming the lower part 2a of the bowl 2 carries a coupling element constituted by a tenon or a cylindrical rod 11, having a groove 11a of semi-circular section, adjacent to one end frustoconical 11b. This coupling rod 11 is engaged in a coupling element formed by a ring 12, of a coupling mechanism 13, this ring and this mechanism of coupling being housed in the tubular part 1a of the rotor 1.

The coupling mechanism 13 includes a coupling means which, in this embodiment, consists by a ring of balls 16 which is located at the end internal of the axial passage formed by the ring 12 secured to the tubular part 1a of the rotor 1. A tubular piston 17 is slidably mounted in the tubular part 1a. Its end upper ends with a funnel-shaped surface 17a. This tubular piston 17 is pressed axially against the inner end of the ring 12 by a spring helical 18 compressed between one end of the part the la of the rotor 1 and a bearing of the tubular piston 17. This axial pressure in the direction of the ring 12 and the funnel shape 17a have the effect of exerting forces centripetals on the crown of balls 16 which presses them into the groove 11a of the coupling stud 11 of the bowl 2.

To prevent these balls from engaging in the opening axial of the ring 12, when removing the post coupling 11, a second piston 14 is slidably mounted inside the tubular piston 17 and a second spring helical 19 pushes it axially against the end of the coupling member 11.

Alternatively, the ring of balls 16 could be replaced by a split ring-type spring piano, or by a coil spring forming a O-ring spring, both ends of which would then brought together by the funnel 17a under the coil spring pressure 18, thereby reducing its diameter to keep it engaged with the groove 11a of the coupling stud.

The outer end of the tubular piston 17 is integral a gripping member 20 intended to allow exercise an axial traction opposite to the pressure of the spring 18, to allow the balls 16 to move outward. The piston 14 subjected to the axial pressure of the spring 19 can then eject bowl 2 upwards and maintain simultaneously the spaced balls 16.

As can be seen in Figure 1, for ensure good tightening of the bowl 2 on the rotor 1, the upper surface of the disc carrying this bowl 2 has a slight clearance 1b, which ensures good contact with the peripheral annular surface of this disc. In addition, the axial position of the groove 11a of the coupling stud 11 can be chosen to be normally still very partially in the axial passage of the ring 12 of so that the engagement of the balls 16 in this groove 11a induces a very slight deflection of the center of the bottom of the bowl 2, which allows the disengagement 1b of the rotor disk 1, thus ensuring sufficient contact between this disc and the bowl 2 to guarantee a friction drive of the latter. In case this friction is not sufficient, radial grooves could be provided for prevent the bowl 2 from sliding relative to the disc rotor 1.

The ball bearings P1, P2 of the tubular part 1a of the rotor are mounted in a support element 21 fixed to a plate 22, itself fixed to an upper disc 26 by four columns 15, two of which are located behind bowl 2 are visible in Figures 1 and 3, the other two being arranged symmetrically with respect to a drive shaft 23 parallel to the axis of the rotor 1. Thanks to this arrangement, the side of the centrifuge opposite the shaft training is free, allowing the introduction side of the bowl 2 and the positioning of the element tubular 9. This allows easy access to the centrifugation 2 and easily carry out its positioning and its removal.

The drive shaft 23 is pivotally mounted through two ball bearings 24, 25, respectively integral with the plate 22 and the upper disc 26 located above the bowl 2. This upper disc 26 is integral with the drive shaft 27 of a motor 28, coaxial to the axis of rotation of the rotor 1. The end of the shaft 23 which extends above the disc 26 is integral with a satellite pinion 29 in engagement with a fixed pinion 30. The ratio between the diameters of the satellite pinion 29 and the fixed gear 30 is 1/1, so that if the speed of rotation of the plate 26 is ω, that of the shaft 23 around its axis is 2ω. The lower end of this shaft 23 carries a toothed pinion 31 connected by a toothed belt 32 to a toothed pinion 33, of the same diameter as the toothed pinion 31, so that the rotor 1 is driven at speed 2ω.

The flexible tubular element 9 forms an open loop one end of which 9a is fixed and coaxial with the pivot axis of the rotor 1. This end 9a is fixed and held in a tubular connector housing 10 'similar to the housing 10 supporting the other end of this element tubular 9. Each of these tubular elements 10 and 10 ' presents a sort of funnel 10a, respectively 10'a (fig. 5) which gives support to this part of the element tubular 9 when subjected to centrifugal force. This loop passes through an opening 22a formed in the plate 22, so that it is driven around the pivot axis of rotor 1 at speed ω, while its end secured to the center of the bowl 2 is driven at speed 2ω and that the other end 9a is fixed, of so that the flexible element is entrained between these two ends at speed -ω around its longitudinal axis canceling any accumulation of torsion between these two ends. This principle is well known since US 3,586 413 of Adams. A support surface 22b secured to the plate 22 serves to limit the deformation of the tubular element 9 under the effect of centrifugal force. Guide parts of the tubular element 9 are preferably made of a material self-lubricating or low coefficient of friction, such as Oilamid®, bronze-Teflon® or Valflon®.

Downstream of the fixed end 9a of the tubular element 9, the three conduits 4a, 5a, 6a separate and the conduit of plasma 6a is associated with a flow control valve 34 depending on the position of the separation surface between plasma and blood cells in the separation chamber 3.

For this purpose, a double prism 3a is formed at the end top of the separation enclosure 3 and came in one piece with the upper part 2b of the bowl 2 during its injection. The portion of this double prism 3a which is covered by the separated blood cells of plasma by centrifugal force following rotation of bowl 2 is opaque, while the part which emerges in the plasma is transparent. An optical device 35 comprising a laser and a photoelectric detector is arranged opposite this prism 3a, so that the detector photoelectric receives the light reflected from the part of the double prism 3a which emerges in the transparent plasma. AT each turn of bowl 2, a proportional duration signal at the angular value of the transparent area of double prism 3a is thus supplied to an amplifier 36 whose outlet is connected to the proportional valve 34. Depending on whether this transparent area increases or decreases, the amplifier 36 will control the proportional valve 34 so that it reduces, respectively so that it increases the section of the plasma evacuation duct 6a, making it possible to maintain by this adjustment, the balance between the flows in the outlet conduits 5a and 6a, depending on a flow rate input determined by the blood supply pump into the conduit 4a, itself determined by the venous pressure from the donor arm.

The dimensioning of the centrifuge bowl 2 and of the tubular element 9 forming the open loop are chosen to reduce the size, weight, the price and volume, both of this bowl 2 and of the whole centrifuge, including sizing is essentially dependent on the diameter of the centrifuge bowl. If the diameter decreases, it is necessary to increase speed. The increase in this may be limited by increasing the height of the centrifuge chamber 3, so that the maximum flow resulting remains practically constant, this being determined by obtaining good cell sedimentation blood.

For example, the diameter of the bowl is 80 mm and its height is substantially equal to its radius. Such diameter corresponds to about a third of that of the rotors of separation of the state of the art. Therefore, the length of the open loop formed by the tubular conduit 9 therefore corresponds substantially to one third of the loops of the state of the art.

By reducing the radius of the bowl 2 and thus the length of the loop formed by the tubular conduit 9, the tensile force exerted on it by the centrifugal force to which it is subjected can be kept at a constant value. Instead of using three pipes of 4 mm in diameter we have a single tubular element 9 of 7 mm in diameter, so that the resulting section is the same, that is to say 0.38 cm ² . The material of the tubular element is plasticized PVC or silicone whose specific weight is 1.2 g / cm ³ , as in the state of the art. Given that the length of the open loop of the tubular element 9 is reduced to a third of that of the prior art, the mass of this tubular element therefore also corresponds substantially to a third. The radius of the open loop is also reduced to almost a third.

The tensile force F exerted on this pipe corresponds to: F = mω 2 .R

In the state of the art we obtain with a loop speed of 1000 rpm (ω ≅ 100) corresponding to half the speed of the rotor which is 2000 rpm and with a loop radius of 0, 13 m, a force of: F = 0.014.100 2 .0.13 = 18.2N

In the case of the example according to the present invention, with a mass of 0.0046 Kg, a loop speed of 3000 rpm (corresponding to a rotor speed 1 of 6000 rpm) and a loop radius 0.045 m, the force is: F = 0.0046.300 2 0.045 = 18.6 N

The value of the tensile forces is: σ = F / S = 18/38 = 0.47 N / mm 2

Since the value of the forces of alternating bending on the tubular element corresponds to: σ = Er / R where r, radius of the tubular element
and R, radius of the loop formed by this tubular element.

The radius R being smaller in the case of the present invention, to decrease σ, it is therefore necessary to decrease r and E. In the example given, E = 4 N / mm ² and σ _rupture = 12 N / mm ² . In the case of bending corresponding to 1 million alternate bending, 5 _^1/2 hours of operation, this value is reduced by a factor of 5 to account for the additional fatigue, so that σ _rupture for bending stress alternating = 2.4 N / mm ² . σ = 4.3.5 / 30 = 0.47 N / mm 2 i.e. a safety factor of 2.4 / 0.47 ≅ 5

This sizing example shows that it is completely made possible to very significantly reduce the diameter of the separation enclosure without loss of performance and without increased constraints as far as some measures are taken to this effect. Now, this reduction in diameter reduces the size of the device so extremely important. This allows to have a device much more compact, lighter and less expensive to manufacture. This device taking up little space, we can install more devices on the same surface, which is important, especially in the case of trucks used for the plasma collection where space is reduced.

By way of example, the rotating part according to the invention weighs about 600 g while the rotors of the devices of the state of the art weigh almost five times what weight. This is the reason why in the collection of blood, plasmapheresis is generally not performed directly but blood is collected in pockets flexible tubes which are then placed in very large centrifuges. In this case, it is no longer possible to return the donor has red blood cells. However, the time for the body reproduce the amount of red blood cells is long, which is why several months must necessarily separate two blood donations for the same donor, this which would not be necessary if red blood cells could be reinjected into it after separation. This is not possible only if the separation is done simultaneously with the blood test.

There are other types of machines that work with a disposable centrifuge bowl, but these require a rotating joint, leading to a more solution expensive and not allowing simultaneous feeding centrifuge liquid and component discharge separated, so it is necessary to alternate supply and discharge, leading to a large volume extracorporeal.

The importance of having centrifuges light and compact and especially loudspeakers disposable separators that can be produced at low cost is so obvious. The ease of changing these speakers or separation bowls is therefore also a need. Only the meeting of all of these conditions may replace current methods of plasma collection.

Another important aspect of this invention is in that the complete circulation of the liquid is obtained by the overpressure with which the blood is brought in the centrifuge bowl 2. This overpressure must compensate for the pressure losses induced in the duct supply 4a as well as in the recovery conduits blood cells 5a and plasma 6a. To create this overpressure can advantageously use a pump peristaltic, intended to ensure the desired flow downstream of the separation. No peristaltic suction pump outgoing components is therefore not necessary, the regulation of the plasma flow being obtained by the regulating valve 34, controlled by its servo system according to the variation of position of the border between the plasma and blood cells.

Of course, if this device is particularly suitable for use to perform online plasmapheresis with the blood test, it can of course also be used in therapeutic applications. We was able to observe in fact that the tubular element 9 containing the three conduits 4a, 5a, 6a is calculated with a factor of security of 5 for continuous use exceeding 5 hours, which allows its use in all applications conceivable.

The apparatus which is the subject of the present invention can also be used for washing blood cells by introducing alternatively with suitable means known in the domain, the cells to be washed and a washing liquid. In variant, the washing liquid could be introduced by an additional conduit, allowing to simultaneously perform separation and washing. In this case, the element tubular 9 should then have four conduits instead of the three represented.

In the variant illustrated in FIGS. 5 and 6, the two discs 22 and 26 of the previous embodiment are replaced by two diametrical arms 22 ', 26' which are come from a single piece of aluminum with two pillars 37 and 38 diametrically opposed. The arm 26 'has a hub 26 'which is driven onto the shaft 27 of the motor 28. The pillar 37 has a cylindrical passage 39 intended for the passage of the drive shaft 23. The other pillar 38 is integral a support 40 having a guide chute 41 of the tubular element 9.

Support 40 is designed to support the element flexible tubular 9 in the area where its radius is greatest large, therefore where the centrifugal force is most important. the funnel 10a supports the central part of the element tubular 9.

To reduce the friction between the chute 41 of the support 40 and the tubular element 9 during the rotation of the device, the support 40 is made, like the support 22b of the embodiment of FIG. 1, made of a material with low coefficient of friction. In addition to the materials already mentioned, we could also use a high weight polyethylene molecular (PEHMW). We can still encourage sliding using when manufacturing the tubular member 9, when the latter is made of PVC, a plasticizer based on silica making its surface more slippery. It is still possible reduce friction by reducing the surface area contact of chute 41 by streaks possibly in form of tendrils.

According to a last variant illustrated by FIG. 7, there are rollers 42 in the support chute 40 freely rotated around axes parallel to that of the element tubular 9. These rollers 42 are driven by the rotation of the tubular element 9 on itself.

The rest of the centrifuge corresponds to the embodiment described above. The variant described in connection with Figures 5 and 6 facilitates balancing and increases the security of the device when rotates at centrifugation speed. It improves also guiding and supporting the tubular element 9, which is thus very little subjected to centrifugal force.

Claims (24)

1. Apparatus for centrifuging a liquid, especially blood, containing particles in suspension, comprising:

   a first driving member (1) mounted so that it can pivot,

   a second driving member (22) mounted so that it can pivot, coaxial with the first driving member (1),

   means (23-33) for driving the said first (1) and the said second (22) driving member, with a ratio of their respective angular rotation speeds of 2:1,

   a member (2) for centrifuging the said liquid, provided with at least three channels (4, 5, 6) connecting its centre to a peripheral separating chamber (3),

   at least three pipes (4a, 5a, 6a) made of an elastically deformable material, each one having a first end secured to the central end of a respective channel (4, 5, 6) of the said centrifuging member (2) and a second end fastened to and coaxially with the first, each pipe (4a, 5a, 6a) forming an open loop around the said centrifuging member (2), a portion of each loop being kinematically secured to the said second driving member (22), one of the said pipes (4a, 5a, 6a) being connected to a source supplying the said liquid to be centrifuged, at least one other serving to recover a component of the liquid,

   first coupling means (16, 17, 17a) secured to the said first driving member (1),

   second coupling means (11) secured to the said centrifuging member (2), and

   elastic means (18) to put the said first (16) and second (11) coupling means in engagement with each other, so as to fasten the centrifuging member (2) to the first driving member (1), characterized in that:

   the said channels (4, 5, 6), the said separating chamber and the said second coupling means (11) are an integral part of the said centrifuging member (2) and in that

   the said first (16, 17, 17a) and second (11) coupling means and the said elastic means (18) are coaxial with the pivoting axis of the said driving members (1, 22), it being possible for the said first coupling means (16, 17, 17a) to be moved along the said pivoting axis in opposition to the pressure from the said elastic means.
2. Apparatus according to Claim 1, characterized in that it comprises a moveable control member (17) connected to the said elastic means (18) such that movement of the control member (17) in opposition to the force exerted by the elastic means makes it possible to detach the said coupling means (11, 16) from each other.
3. Apparatus according to Claim 1, characterized in that the said elastic means (18) drive a moveable piston (17) engaged with the first coupling means (16) causing the first and second coupling means (16, 11) to come into contact.
4. Apparatus according to Claim 1, characterized in that the said second coupling means (11) exert, on the said elastic means (18), a force which is greater and in the opposite direction to that which tends to bring the said first (16) and second (11) coupling means into engagement with each other when putting the said centrifuging member (2) in place on the said first driving member (1).
5. Apparatus according to Claim 1, characterized in that the first driving member (1) comprises an axial through-passage and the first coupling means (16) are a ring of balls placed circumferentially inside the axial through-passage of the said first driving member.
6. Apparatus according to Claim 5, characterized in that the second (11) of the said coupling means comprise a frustoconical end (11b) for temporarily moving the said ring of balls (16) in a generally radial direction when the second coupling means (11) are inserted into the axial through-passage.
7. Apparatus according to Claim 5, characterized in that the centrifuging member (2) comprises a lower part (2a) and the second coupling means (11) consist of a rod projecting from the lower part (2a) of the centrifuging element (2), the rod having a circumferential groove (11a) dimensioned in order to accommodate a portion of the said ring of balls (16) when the centrifuging member (2) is mounted on the first driving member (1).
8. Apparatus according to Claim 7, characterized in that it comprises a first moveable piston (17) coupled to the said elastic means (18) such that the movement of the said first piston (17) in the direction away from the force exerted by the said elastic means (18) makes it possible to separate the first coupling means (16) from the second coupling means (11).
9. Apparatus according to Claim 8, characterized in that the first piston (17) has a funnel-shaped surface (17a) such that, following application of the axial force by the said elastic means (18), the first piston (17) subjects the said ring of balls (16) to a centripetal force, thus fastening the centrifuging element (2) to the first driving member (1).
10. Apparatus according to Claim 9, characterized in that it comprises a grasping member (20) secured to the said first piston (17) in order to allow this first piston (17) to be moved in opposition to the said elastic means (18), thus separating the funnel-shaped surface (17a) of the first piston (17) from the ring of balls (16), freeing them from the centripetal force.
11. Apparatus according to Claim 10, characterized in that a second piston (14) is mounted so that it can slide inside the said first piston (17), second elastic means (19) pushing this second piston (14) in the direction of the inner end of the said axial through-passage (12), the travel of this second piston (14) being chosen to make it enter the said axial through-passage (12) when separating the said centrifuging member (2) from the said first driving member (1) and in order to retain the said ring of balls (16) in the said funnel (17a) of the said first piston (17).
12. Apparatus according to Claim 11, characterized in that the pressure exerted on the second piston (14) by the said second elastic means (19) is capable of ejecting the said centrifuging member (2) when separating the said first and second coupling means (11, 16).
13. Apparatus according to Claim 1, characterized in that one (6a) of the said pipes designed to be connected to a collector of one of the components coming from the centrifuging comprises a proportional valve (34), detecting means (35) being placed upstream of this pipe (6a) in order to measure the degree of purity of the component having to flow through the said pipe, this detector being connected to the said proportional valve (34) in order to adjust the flow rate in the said pipe (6a) as a function of the said measured degree of purity.
14. Apparatus according to Claim 6, characterized in that a double prism (3a) is placed in the said separating chamber (3), the said detecting means (35) comprising a light beam, which is fixed with respect to the said centrifuging member (2), directed along the path of this double prism (3a) and a photoelectric detector for measuring the angular value of the portion of this double prism emerging from the layer of blood cells in the plasma and for delivering a signal characteristic of this angular value to a member (36) for controlling the said proportional valve (34).
15. Apparatus according to Claim 1, characterized in that a space is made laterally in the said first and second driving members (1, 22) in order to allow the said centrifuging member (2) to pass through.
16. Apparatus according to one of the preceding claims, characterized in that the said circular centrifuging member (2) comprises two parts (2a, 2b) assembled to each other in a sealed manner and in that the said three pipes (4a, 5a, 6a) form a single tubular element in which three separate pipes are made, one end of this tubular element being fastened in a sealed manner coaxially to the axis of rotation of the said centrifuging member (2).
17. Apparatus according to one of the preceding claims, characterized in that the parts of the apparatus in contact with the said tubular element (9) are made of a self-lubricating material or a material with a low coefficient of friction.
18. Apparatus according to one of the preceding claims, characterized in that it comprises a fourth pipe, two of which are connected respectively to a pressurized source of red blood cells and another to a pressurized source of liquid for washing these red blood cells.
19. Apparatus according to one of Claims 1 to 18, characterized in that one of the said pipes (4a, 5a, 6a) is alternately connected to a pressurized source of red blood cells and to a pressurized source of liquid for washing these red blood cells.
20. Apparatus according to one of the preceding claims, characterized in that the said second driving member (22') and an element (26'), secured to the means (27, 28) for driving this second driving member, form one and the same piece.
21. Apparatus according to one of Claims 1 to 3, characterized in that radial serrations for increasing the friction force are made on at least one of the surfaces in contact with the said first driving member (1) and the said centrifuging member (2).
22. Apparatus according to Claim 1, characterized in that one (1) of the said members assembled by the said coupling means (11, 16) comprises an axial through-passage (12) on an internal end of which is placed coaxially a ring of balls (16), in that the other (2) of the said coupling means comprises a peg (11) whose diameter corresponds to that of the said axial through-passage (12) and whose length exceeds that of this through-passage, the part of this peg (11) projecting from this axial through-passage (12) comprising an annular groove (11a), dimensioned in order to partially accommodate the said ring of balls (16) and adjacent to a frustoconical end (11b) of this peg (11), and in that a tubular piston (17), one end of which has the shape of a funnel (17a) shaped in order to accommodate the said ring of balls (16), is associated with the said elastic means (18) in order to press this piston (17) axially in the direction of the end of the said through-passage (12) adjacent to the said ring of balls (16) in order to apply this ring (16) thereto by exerting a centripetal pressure on it so as to press the said balls (16) into the said annular groove (11a), a grasping member (20) being secured to the said tubular piston (17) in order that it can be moved in opposition to the said elastic means (18).
23. Apparatus according to Claim 1, characterized in that the said first and second coupling means (1, 2) comprise, on the one hand, a split annular elastic element (16), placed coaxially on an inner end of an axial through-passage (12) of this first driving member (1), the section of which is less than the diameter of this elastic element (16) and a tubular piston (17), one end of which has the shape of a funnel (17a) shaped in order to accommodate the said element (16), the said elastic means (18) axially pressing this piston (17) in the direction of the inner end of the said through-passage (12) in order to apply the said split annular elastic element (16) thereto by clamping it radially so that its inner diameter is less than that of the said through-passage (12), a grasping member (20) secured to the said tubular piston (17) in order to move it in opposition to the said elastic means and, on the other hand, a peg (11), whose section is the complement of that of the said through-passage (12), this peg (11) having a groove (11a) located at the exit of the said through-passage (12) in order to accommodate the said split annular element (16) and adjacent to a conical end (11b) designed to allow this split annular element (16) to open on inserting this peg (11) into the said axial through-passage (12), in order to bring the said groove (11a) opposite this split annular element (16) so as to allow it to engage thereon and to fasten this centrifuging member (2) to the driving member (1), and in that a grasping member (20) is secured to the said tubular piston (17) to allow it to be moved in opposition to the said elastic means (18).
24. Use of the centrifuging apparatus according to one of the preceding claims, characterized in that the liquid to be centrifuged is placed at a pressure chosen to overcome the pressure drops and to provide the desired flow rate of the said liquid.

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