Abstract:
Apparatus ( 1 ) includes a device ( 20 ) for moving at least one compartment ( 2 ) in the apparatus, the compartment forming a support for tubes ( 3 ), which apparatus further includes elements ( 50 ) for taking a specimen of a product contained in the tubes, the movement device ( 20 ) including elements ( 21 ) for guiding the compartment during movement of the compartment and further including stirring members ( 27 ) for the guiding elements, the movement device being mounted on a chassis ( 4 ) of the apparatus.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to devices for handling racks for tubes in an analysis apparatus, in particular an automatic blood analysis apparatus. 
     The present invention also relates to associated methods for moving said racks in the apparatus. 
     Hereafter reference will be made essentially to the analysis of blood samples. However, this must not be considered as limitative. 
     In view of the analysis, the samples, in particular the blood samples are generally contained in tubes. Each tube is hermetically sealed by a stopper which may be pierced. Taking a specimen from the tube is carried out through the stopper, using a sampling needle. For ease of handling, these tubes are arranged in racks. Each rack can for example contain 5 tubes arranged side by side, parallel and substantially in the same plane. 
     During the movement of a rack in the apparatus, the rack can be subjected to several handling operations. Generally, these handling operations are:
         the loading of the rack into the apparatus;   the unloading of the rack, once analyses have been carried out;   the movement of the rack in the apparatus, in particular between a loading position, an analysis position and an unloading position; and,   the agitation of the contents of the tube, with a view to its homogenization. Such homogenization is particularly useful in the case of blood samples, in order to ensure that the sample specimen taken from a tube is truly representative of the contents of the tube.       

     Most automated haematology devices use horizontal loading devices. These devices are bulky, expensive and complex. They may moreover, due to their complexity, present problems of reliability. Such loading devices are described in the documents FR2692358 and FR2812088. 
     Other automatic devices use magnetic vertical loading. Such magnetic loading, in particular described in the document U.S. Pat. No. 4,609,017, requires a metal plate to be fixed onto each rack and uses a pneumatic device to load or unload a rack by a movement from the bottom upwards. 
     In such loading devices, it is not possible to ensure the agitation of the tubes. 
     The movement of the racks in an automatic analyzer is generally done linearly, the tubes being substantially vertical and their stopper being at the top. The rack therein is generally guided by rails. In such movement devices, it is not possible to ensure the agitation of the tubes. The document U.S. Pat. No. 4,609,017 describes a movement device using a conveyor belt which also serves as an agitation device. This solution does not allow perfect homogenization. The device is expensive and remains of limited reliability. 
     For the agitation, apart from the conveyor belt, other devices are described in the documents U.S. Pat. No. 4,921,676, FR2692358, FR2730315, FR2812088, U.S. Pat. No. 4,518,264. They make it possible to agitate one or more tubes removed from a rack, or a rack containing tubes. These devices are expensive and complex. Indeed, they require a mechanism dedicated to agitating the rack or the tubes in the movement device, and a mechanism for withdrawing them, before agitation, then returning them, after agitation. 
     Once the necessary sampling operations have been carried out in the tubes of a rack, the rack is arranged in a receptacle provided for this purpose. Such devices are described in the documents FR2692358 and FR2812088. The document U.S. Pat. No. 4,609,017 describes a vertical ejection system moved by a pneumatic device. 
     SUMMARY OF THE INVENTION 
     The purpose of the invention is to propose at least one simplified, reliable and effective device among devices allowing the handling of racks in an automated analysis apparatus. Moreover, such a device can preferably be used in an automated apparatus suitable for use in small laboratories. 
     Another purpose of the invention is to propose at least one method for handling racks, suitable for use by a device according to the invention. 
     Yet another purpose of the invention is to propose an apparatus, in particular an automated blood analysis apparatus, comprising a device according to the invention and/or implementing a method according to the invention. 
     According to a first objective of the invention, such an apparatus comprises a device for moving at least one rack in said apparatus, said rack forming a support for tubes, an apparatus further comprising means for taking a specimen of a product contained in said tubes, said movement device comprising means for guiding the rack during movement of said rack and further comprising means for agitating the guiding means, said movement device being mounted on a chassis of said apparatus. This apparatus is particularly suitable for being an automated product analyzer, in particular an automated blood analyzer. 
     Advantageously, the guidance means are means for holding the rack in the apparatus, such that during agitation, the rack is correctly held in the apparatus. The guidance means can be a rail cooperating with a complementary shape of the rack. This rail can have a C-shaped cross-section, two opposite ends of which extend towards each other and each forming a rib, said ribs being provided to engage with respective grooves on either side of a rack. Such an arrangement allows the rack to be held at the same time as it is guided, by the cooperation of the ribs and the complementary shapes, for example grooves, in the rack. 
     The movement device can comprise worm means for cooperating with a complementary shape of the rack, for example a nut, preferably partial. A stepping travel motor can be provided for driving the worm means in rotation. Thus, it is possible to know at any moment the position of a rack in the apparatus, which guarantees, in an analyzer, certain knowledge of the contents of whichever tube is being analyzed. 
     Preferably, the movement motor is mounted rigidly connected to the guidance means. Thus, the agitation of the rack does not cause a relative rotation of the worm or worms with respect to the guidance means, there is therefore a movement of the rack along the guidance means, for example along the rail. 
     The agitation means are preferably designed to allow a rotation of the rack about an axis parallel to a direction for the movement of the rack, for example in order to allow the rocking of the tubes between a position directed downwards close to the vertical, and a position, directed upwards, close to the vertical, such agitation making it possible to reproduce, with similar efficiency, the agitation which can be done manually by an operator. 
     For complete automation, an apparatus according to the invention advantageously comprises a loading device and/or an unloading device for the rack, said devices being advantageously fixed onto the chassis of the device. 
     The loading device can comprise a storage element for stacking several racks therein. The storage element can be designed to allow the movement under gravity of a rack in the storage element. Within the framework of a “first in/first out” type of operation, the loading device can comprise means for removing the lowest rack from the stack in the storage element. 
     The removal means can comprise a worm provided for engaging with a complementary shape of the rack, for example a nut-type shape, and a loading motor, preferably of the stepping type, for driving the worm. 
     The worm advantageously comprises a truncated zone in which the worm threads are interrupted beyond a plan parallel to the axis of rotation of said worm, said truncated zone being provided in order to allow a rack to adopt a position such that the worm, after rotation about said axis, can engage with said rack. 
     An unloading device for an apparatus according to the invention advantageously comprises a receptacle for unloaded racks. The movement device can be provided to move a rack right into a zone for receiving the receptacle. 
     The receptacle advantageously extends, for example on one side of the apparatus, following a substantially horizontal direction and substantially perpendicular to an axis of movement for a rack, in the movement device, and in that it further comprises means for displacing each rack a distance at least equal to the thickness of said rack, in the direction of extension of the receptacle. These displacement means can comprise one or more cams moved by a stepping motor. 
     A system, in particular a blood analysis system comprising an apparatus according to the invention and equipped with worm means for moving the rack, advantageously includes a rack comprising recesses together forming a portion of a nut for cooperating with the worm means. Such a rack can moreover be of the closed type, i.e. having a sampling wall opposite stoppers in the tubes, said sampling wall being pierced with openings allowing the penetration of a sampling needle. 
     According to a second objective of the invention, a method for handling a tube in an apparatus, said method comprises:
         the arrangement of the tube in a rack provided to serve as a support for said tube;   the use of guidance means for guiding and holding the tube in the apparatus; and,   rocking the guidance means.       

     Such a method is advantageously used to allow the movement of the tube and the homogenization of a blood product contained in the tube, with a view to the analysis of this blood product. 
     Other features and advantages of the invention will also become apparent from the description below, which relates to non-limitative examples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the attached drawings: 
         FIG. 1  is a three-quarter front perspective view of an automatic analyzer according to the invention; 
         FIG. 2  is a general and a three-quarter front perspective view of a loading device of the automatic analyzer of  FIG. 1 ; 
         FIG. 3  is a general and a rear three-quarter perspective view, on a reduced scale, of the loading of the automatic analyzer of  FIG. 2 ; 
         FIG. 4  is a rear three-quarter perspective view of a translation and agitation device of the automatic analyzer of  FIG. 1 ; 
         FIG. 5  is a perspective view from the front and from above of the translation and agitation device of the automatic analyzer of  FIG. 4 ; 
         FIG. 6  is a profile and perspective view of the translation and agitation device of the automatic analyzer of  FIG. 4 ; 
         FIG. 7  is a diagrammatic illustration of the loading of the rack of 
         FIG. 6  into the automatic analyzer of  FIG. 1 ; 
         FIG. 8  is a perspective view of a rack suitable for use in the automatic analyzer of  FIG. 1 ; 
         FIG. 9  is a diagrammatic illustration of the guiding and holding of the rack of  FIG. 8  in the automatic analyzer of  FIG. 1 ; 
         FIG. 10  is a perspective view of a first embodiment of an unloading device for the automatic analyzer of  FIG. 1 ; and, 
         FIGS. 11 and 12  are two perspective views of a second embodiment of an unloading device for the automatic analyzer of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  represents an automated blood analyzer  1  according to the invention. This automatic analyzer allows the handling of racks  2 . As particularly illustrated in  FIG. 8 , each rack  2  is provided to contain five tubes  3 , each containing a product, in this case a blood product, to be analyzed. The automatic analyzer  1  comprises a loading device  10 , a movement and agitation device  20  and an unloading device  30  for the racks  2 . The unloading device is only partially represented in order to simplify  FIG. 1 . The movement device  20  is provided to allow the movement of a rack from a loading position to an unloading position, by passing through an intermediate sampling position for a blood specimen in one of the tubes. The movement device further comprises agitation means  27 , provided to allow the agitation of the tubes with a view to the homogenization of their content before sampling. 
     The automatic analyzer  1  further comprises a sampling device  50 , in particular a needle  51 , for the sample, partially represented in  FIG. 1 , and means of analysis, not shown, for the specimen taken. 
     The automatic analyzer  1  further comprises a chassis  4  bearing in particular all of the devices and means  10 , 20 , 30 , 27 , 50  mentioned above as well as the analysis means. 
     A rack  2  which can be used in the automatic analyzer of  FIG. 1 , is now more particularly described with reference to  FIGS. 7 and 8 . The rack  2  illustrated is in the form of a box. This box comprises a back  61  and four side walls  62 , 63 , 64  around, and perpendicular to, the back  61 . The rack  2  illustrated is envisaged to contain up to five tubes  3 ; it is here shown full. The tubes  3  are detachably snapped onto the back and parallel to it. The rack  2  is completely open opposite the back  61 , such that the tubes can be easily introduced into the rack or removed from it. The side walls extend from the back over a substantially constant distance, constituting a thickness E 2  for each rack. In the example illustrated in the figures, the racks are provided identical to each other. 
     Among the side walls, a sampling wall  62  is arranged facing the stoppers  6  of the tubes  3 . The sampling wall  62  is pierced through with sampling openings  67  (see particularly  FIGS. 2 ,  4  and  6 ). Each opening  67  being arranged to be opposite a stopper  6  of a tube  3  in the rack  2 , such that the sampling needle  51  can be introduced through the opening  67  then through a respective stopper  6  to take a sample from a given tube, as illustrated in  FIG. 1 . 
     Another side wall  64 , opposite the sampling wall  62 , forms a basis  64  for the rack. The external surface of the basis  64  comprises recesses  65  extending from the back  61 , transversally to the projection, such that the recesses  65  together form part of a nut, capable of engaging with a worm, for the movement of the rack in the automatic analyzer. The rack  2  further comprises, on either side of the basis  64 , slots  66  in the side walls  63 , slots parallel to the basis  64  and provided to engage with a guide rail  21 , for guiding in translation the rack in the automatic analyzer (see in particular  FIG. 9 ). 
     The loading device  10  will now be described more particularly with reference to  FIG. 2 . In the example illustrated, the loading device comprises a storage element  11 , provided to allow the substantially vertical stacking of several racks  2  stacked on top of each other, in a loading position. 
     The storage element  11  is slightly inclined towards the rear. Thus, a rear wall  110  of the loading device  11  forms a ramp  110  inclined such that the basis  64  of each rack  2  remains supported against the ramp, which allows correct positioning of the projection, the movement of the rack in the storage element being achieved by gravity. 
     In the loading position, the back  61  is above the tubes and the sampling wall  62  is oriented towards the front of the automatic analyzer. The loading device operates according to the principle “first in/first out”, i.e. it is the rack underneath the stack, in a so-called bottom position, which is removed from the loading device in order to analyze its contents. The movement of any racks  2  not yet removed is achieved by gravity, until the bottom position is reached.  FIG. 2  represents a rack in the process of being removed, the other racks contained in the storage element progressively taking up their new position in the storage device. 
     Means  13 ,  14  for removing the racks from the storage device  11  will now be described. The removal means comprise a loading motor  13  and a loading worm  14 , with a horizontal axis X 14 . The worm  14  is envisaged to be driven by the motor  13 . The motor is a stepping motor. 
     The worm  14  is arranged at the rear of the storage element, such that it can engage with the recesses  65  (see  FIG. 8 ) of a rack when the latter is in the bottom position. As illustrated in  FIG. 7 , the worm  14  comprises a truncated zone  141 . In the truncation zone  141 , beyond a plane P 141  parallel to its axis of rotation X 14 , the threads of the worm are interrupted. Thus, in a position as illustrated in  FIG. 7 , in order to allow the descent in the direction of D of a rack  2  into the bottom position in the storage element, the truncation zone is arranged towards the front relative to the axis X 14 . This arrangement allows a rack to take up the bottom position without being obstructed by the presence of the worm  14 . When the rack has taken up the bottom position, the rotation of the worm  14  by the motor  13 , allows the removal of the rack in order to introduce it into the movement and rocking device  20 . The pitch of the worm  14  is oriented such that the rack in process of being removed is pushed downwards onto a plate  15 , which forms a base for the storage element  11 . The plate  15  serves as a reference for positioning relative to the movement device  20 . 
     The movement device  20  is in particular shown isolated from the rest of the automatic analyzer  1 , in  FIGS. 4-6 . The movement device  20  is structured about an axis of movement X 20  which merges with the loading axis X 14 . As illustrated in  FIG. 1 , it extends at the front of the automatic analyzer and transversally to the automatic analyzer, between a proximal end  201 , adjacent to the loading device  10 , and a distal end  202 , adjacent to the unloading device  30 . 
     The movement device  20  comprises means for guiding in translation  21 . As particularly illustrated in  FIG. 9 , the guidance means form a rail  21  having a substantially C-shaped section transversal to and around the axis X 20 . Ends of the C extend towards each other and each form a rib  211 . The ribs are provided to engage in the grooves  66  of a rack  2 , each of the ribs  211  on a respective side of the projection  64  of the rack  2 . The rail  21  comprises an internal surface  212  forming a portion of a cylinder coaxial with the axis X 20 . In order to allow the mounting of the movement device, by way of example, in the example illustrated, the rail is formed in two symmetrical parts along a plane containing the axis of movement X 20 . 
     The movement device  20  further comprises means of movement by worms  22 ,  23 ,  24  for driving the rack in transversal movement along the rail  21 . These worm means comprise several worms  22 ,  23 , mounted on a drive shaft  25 , coaxial with the axis X 20 . A first  22  of the worms is arranged in the immediate vicinity of the proximal end  201 ; a second  23  is arranged in the immediate vicinity of the distal end  202 . 
     The worms  22 ,  23  are mounted in rotation within the internal face  212  of the rail  21 . The shaft  25  is borne by bearings  213  formed in two parts, each of a single piece with a respective part of the rail. The shaft  25 , and the worms that it bears, are driven in rotation by a travel motor  24 . The travel motor is mounted fixed relative to the rail  21 . The travel motor is advantageously a stepping motor. 
     The movement device  20  further comprises agitation means  27 . The agitation means  27  comprise a gear pinion  28  driven by a motor  29 . The gear pinion  28  is a toothed sector forming an angle greater than 180°. The toothed sector is centred on the axis of movement X 20 . It is mounted rigidly fixed to the rail  21 , and, in the example illustrated, it is made of a single piece with at least one of the parts of the rail  21 . 
     During the removal of a rack  2  from the storage element  11 , the rail  21  is arranged such that the removed rack engages with the rail, i.e. the ribs  211  engage with the slots  66  of the rack  2 . The worm  14  of the loading device  10  moves the rack during the process of removal until it engages with the rail. The first movement worm  22  comprises at its proximal end a truncation  221  similar to the truncation  141  of the worm  14 . When the rack has advanced sufficiently on the rail, along the truncation  221  of the movement worm  22 , the first movement worm  22  is rotated and engages with the projection  65  of the rack  2  which it drives along the truncation  141  of the worm  14  until it is completely removed from the storage element  11  then, continues along the rail  21 . 
     Once completely removed and taken up by the movement device  20 , the rack can be agitated to allow the homogenization of its contents. For the agitation, the agitation means  27  is used, i.e. the rail is caused to rotate about its axis X 20 , and thus the rack borne by the rail is caused to tilt. Thus, the rack which has been removed substantially horizontally from the loading element  11  can be tilted downwards, such that the tubes contained are positioned stopper downwards, or tilted upwards, i.e. that the tubes are positioned stopper upwards. Thus, by an alternating downward and upward movement, it is possible to agitate the tubes with a movement similar to that which can be produced manually by an operator. This movement is therefore particularly effective. The ribs  211  of the guidance means, in engagement with the grooves  66  of the rack  2 , ensure the rack is held in the movement device  20 , therefore in the automatic analyzer, during its movement or of its agitation, whatever the position of the rack about the axis of movement X 20 . 
     The combined use of the means of movement by worm and means of rocking also makes it possible to bring the rack into a high position, tilted slightly towards the rear, as illustrated in  FIG. 1 , a position in which the sampling needle  51  can penetrate the stopper  6  of a tube  3  arranged opposite the needle  51  in order to take a blood specimen from it. 
     In a preferred embodiment, it is possible to interrupt the automatic operations and bring the rail into a low position, not shown, which means that the rack or racks optionally borne by the rail are directed downwards. There is then free access to the needle and an operator can manually present a single tube in order to take a sample from it. The needle is mounted on a swinging arm  52  articulated about a horizontal axis X 50 , such that the needle can be tilted towards the front in order to facilitate sampling from the isolated tube. 
     The rail is long enough for several racks, two racks in the example illustrated, to be simultaneously engaged with the rail, whilst allowing it to tilt. During the introduction of a new rack, the previous rack can be brought towards the loading device, such that the newly removed rack fits close to the previous rack. Thus, the position of the following rack is perfectly known relative to that of the previous rack. Moreover, due to the fact that the movement motor is rigidly fixed to the rail, the rocking does not cause any rotation of the worm means  22 ,  23  relative to the rail  21  and each rack remains immobile in translation during the rocking. Moreover, the use of a stepping motor, in particular for the movement motor, makes it possible to move the racks  2  on the rail  21 , knowing the position of each tube at any moment. Thus, the racks can be successively moved in the automatic analyzer, from the loading device  10 , as far as the unloading device  30 , without any risk of mistaking a tube. 
     In particular, it may be useful to carry out a new analysis on the contents of an already analyzed tube, for example in order to check a result, when said already analyzed tube is arranged in a rack preceding a rack being analyzed. The time necessary to obtain the results of an analysis is shorter than the time necessary for taking the specimens from the tubes contained in a single rack. Thus, as the previous rack is still on the rail, it is possible, by reversing the rotation of the movement worms  22 ,  23 , to move back the previous rack for a new analysis. Thanks to the precision of positioning, the already analyzed tube will be analyzed once again with the certainty of not mistaking the tube. 
     After the analysis of the tubes contained in a rack, the rack can be removed from the automatic analyzer in order to be reused subsequently, with new tubes. An automatic analyzer according to the invention advantageously comprises an unloading device  30 , as partially illustrated in  FIG. 1 , and two embodiments of which are illustrated in  FIG. 10  and in  FIGS. 11 ,  12  respectively. 
     A first embodiment of an unloading device  30  illustrated by  FIG. 10  will be described first. The unloading device  30  comprises a receptacle  31  for receiving the racks already analyzed. In  FIG. 1 , only the receptacle  31  is represented. The receptacle  31  is arranged on the right of the automatic analyzer  1 , in the vicinity of the distal end  202  of the movement device  20 . It comprises a receiving zone  35 , situated at the front of the receptacle  31 , for receiving the racks immediately upon leaving the movement device  20 . The receiving zone  35  is in the immediate vicinity and in alignment with the distal end  202 . The receptacle  31  extends substantially horizontally, from the receiving zone  35  towards the rear of the automatic analyzer. The receptacle is provided for receiving the racks arranged vertically, the basis  64  oriented downwards and the backs  61  of the racks being orientated towards the rear, such that the thickness E 2  of the racks extends horizontally, from the front to the rear. 
     In the embodiment particularly illustrated in  FIG. 10 , the unloading device  30  further comprises displacement means  32 , for the successive displacement of the racks unloaded from the receiving zone towards the rear of the receptacle  31 . The displacement means  32  comprise two cams  33 . The two cams are mounted in rotation about a horizontal cam axis X 33 . The cam axis  33  is substantially parallel to the axis of movement X 20 . The cams are moved in rotation about the cam axis X 33  by a stepping motor, not shown in  FIG. 10 . The cams  33  are provided to be supported simultaneously, each against a respective side wall  63  of a rack in the receiving zone  35 . The, cams are identical to each other. Each cam is in the form of an disc which is off-centre relative to the cam axis X 33 , such that the distance D to the axis X 33  varies at least between a short distance to the axis D 1  and a long distance to the axis D 2 , the difference D 2 -D 1  being equal to the thickness E 2  of a rack  2 . 
     The unloading of a rack from the movement device  20  is carried out when the rack to be unloaded is tilted vertically upwards, i.e. when the sampling wall is oriented upwards. Moreover, in order for the receiving zone to be freely accessible, the cams must, prior to the unloading, be arranged such that they have, opposite the receiving zone  35 , a distance D 3  to the axis X 33  less than or equal to the short distance D 1 . By the action of the second movement worm  23  on its basis  64 , the rack to be unloaded is brought into the receiving zone  35 . Then, the cams are rotated such that the distance D to the axis X 33 , opposite the receiving zone  35  progressively increases. When the distance reaches D 1 , the cams come into contact with the rack and begin to displace it towards the rear of the receptacle  31 , until the distance D reaches or exceeds the distance Dl. The receiving zone is then cleared once again, ready for the unloading of a new rack. Each rack displaced by the displacement device is supported on any previously displaced rack, progressively forming a line of unloaded racks. The receptacle  31  is advantageously designed in order to be able to receive a number of racks at least equal to the number of racks provided to be stored in the storage element  11 . 
     A second preferred embodiment of an unloading device  30  illustrated by  FIGS. 11 and 12  will now be described, essentially to the extent that it differs from the embodiment illustrated in  FIG. 10 . In this second embodiment, the receiving zones  35  and the receptacle  31  are similar to those previously described. By contrast, the displacement system  70  used here is a pallet system  70 . The displacement system  70  comprises a pallet  71  formed from a single piece with a casing  72 . The casing and the pallet are formed and arranged such that the pallet extends substantially from the casing, upwards, above the receiving zone  35 , and the casing  72  extends downwards, from the pallet, below the receiving zone  35 . The casing is freely articulated about a pallet axis X 70 . The pallet axis X 70  is substantially parallel to the axis X 20 . The axis X 70  is arranged through the bottom part of the casing. 
       FIG. 11  illustrates a standby position for the thrust system  70 .  FIG. 12  illustrates a thrust position for the thrust system. The thrust system is mounted mobile in rotation about the axis X 70 , between the waiting position and the thrust position. The movement of the thrust system between the two positions is ensured by tilting means  73 . These tilting means comprise an eccentric  74  mounted in rotation about an axis of the eccentric X 74 , parallel to the pallet axis X 70 . The eccentric is driven in rotation by a motor  75 . It is mounted inside the casing  72 , between two opposite walls of said casing, such that its rotation, supported on the opposite walls, causes the tilting of the casing, and therefore of the pallet  71 . 
     The pallet has a connecting zone  712  with the casing  72 , formed such that, in the standby position, the connecting zone  712  forms a flat and vertical wall which serves as a guide, at the front of the receiving zone  35 , for a rack  2  introduced by the movement means  20  into the receiving zone  35 . In the standby position, a thrust zone  711  of the pallet  71  forms a flat wall extending from the connecting zone upwards and forwards from the connecting zone  712 . The thrust zone  711  is formed such that in the thrust position, the thrust zone is vertical, and arranged beyond the receiving zone rearwards. 
     Thus, when a rack is introduced into the receiving zone  35 , it is first guided by the connecting zone  712 . Then, when the rack is completely in the receiving zone, i.e. in particular it is no longer engaged with the guidance device  20 , the rocking of the pallet towards the rear as far as the thrust position makes it possible to bring the rack onto the receptacle  31 , by pushing any racks previously unloaded and simultaneously freeing the receiving zone  35 . 
     Of course, the invention is not limited to the examples which have just been described, and numerous adjustments can be made to these examples without exceeding the scope of the invention. 
     In particular, the automatic analyzer can be envisaged to be used with other types of rack, in particular racks provided in order to contain a number of different tubes, or open racks, i.e. with no wall opposite the stoppers. 
     Instead of a loading of the racks by gravity, mechanical loading can be provided, for example horizontal, for example with thrust means similar to the unloading means, or by the action of a spring. 
     The agitation can also be provided by any rotation, possibly even up to 360°. It is however preferable to ensure at least one 180° rocking movement, between a position close to the vertical upwards and a position close to the vertical downwards. 
     The idea of the rail must be understood in the broad sense. For example, the function of the rail can be ensured by at least partially magnetic guidance and holding means.