Patent Publication Number: US-10322419-B2

Title: Dual centrifuge rotor with damping mass

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This patent application is the national phase entry of PCT/EP2015/077540, international application filing date Nov. 24, 2015, which claims the benefit and priority of and to German patent application no. 10 2015 100 613.8, filed Jan. 16, 2015. 
     PCT/EP2015/077540, international application filing date Nov. 24, 2015 and German patent application no. 10 2015 100 613.8, filed Jan. 16, 2015 are incorporated herein by reference hereto in their entireties. 
     FIELD OF THE INVENTION 
     The invention relates to a dual centrifuge rotor. 
     DESCRIPTION OF THE RELATED ART 
     EP 2 263 654 A2 discloses a method for producing lipid-based nanoparticles as well as to kits and accessories for producing the lipid-based nanoparticles by way of homogenization in a dual asymmetric centrifuge. As may be gathered from this printed publication, better results are achieved if the longitudinal axis of a sample container containing the materials for producing the lipid-based nanoparticles is arranged at an angle, preferably an angle ranging from 70° to 110°, to an axis of rotation of a rotary unit. Frequently, the dual centrifuge includes two or plural rotary units so as to enable the centrifuge to accommodate a higher number of sample containers and thus process a higher number of samples simultaneously. The homogenization of materials, as well as the mixing or grinding of samples, in sample containers which preferably have their longitudinal axis aligned at an angle of between 70° and 110°, relative to the axis of rotation of a rotary unit, is effected by the rapid movement of the materials in the sample containers, as a function of the respective position of the containers relative to the centrifugal force of the dual centrifuge. These rapid movements of material in the containers will result in uneven loads, and thus imbalances, in the dual centrifuge. 
     The high rotary speeds required for numerous homogenization, mixing or grinding processes then result in correspondingly large mass imbalances. The orientation of the sample containers may be a major cause for imbalances in the rotor. If the longitudinal axis of the sample container is not aligned concentrically with or parallel to the axis of rotation of the rotary unit, there will be a higher risk of imbalances occurring in the rotor. On the other hand, an asynchronous arrangement of the sample containers in the individual rotary units will increase the adverse effect of the mass imbalances since the mass movements in the sample containers cannot possibly be synchronous. 
     These imbalances which are required for the process not only result in noise and disruptive vibrations but also lead to premature wear and tear of mechanical components—which adversely affects the safety of the centrifuge and results in unnecessary costs. Moreover, the quality of the sample material to be produced is also compromised by the presence of imbalances in excess of the extent necessary. For this reason, the required process imbalances will have to be reduced, or compensated, to the required extent. 
     EP 2 263 653 A2 and FR 2 955 042 A1 each disclose asymmetric centrifuges. In these cases, masses are inserted in the rotor for balancing the asymmetric loads. However, the subject matter of the present application is a symmetric centrifuge, so the present invention aims at solving a different kind of problem. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide a rotor of a dual centrifuge which avoids the abovementioned shortcomings and in which the required mass shifts for the process and the resulting imbalances in the sample containers do occur, in which the imbalances of the overall rotor unit do not exceed a technically acceptable extent, however. 
     The invention is based on the finding that the overall mass of the rotor can be increased by using additional damping masses and/or by aligning the sample container receptacle and hence the sample containers in an identical manner relative to the rotor and thus synchronizing the movement of the at least two rotary units present as optimally as possible. 
     As a matter of fact, these findings do not relate exclusively to the production of lipid-based nanoparticles, but generally to rotors used in dual centrifuges. Some important processes here are the grinding and/or the mixing of samples, for example. 
     According to the invention, a dual centrifuge rotor which is adapted to rotate about a main axis of the centrifuge comprises at least two rotary units that are arranged symmetrically to one another and each have a bearing and a rotary head which is connected to the bearing and which is mounted in the bearing so as to be rotatable about an axis of rotation. The rotary heads can be driven to rotate about the axis of rotation relative to the rotor by another rotary mechanism of the centrifuge, and have a rotary head receiving unit for at least one sample container and/or at least one sample container receptacle. The axis of rotation of the rotary unit of the rotor is inclined relative to the drive axis of the rotor. The rotary head receiving unit is designed to receive an elongated sample container receptacle and/or an elongated sample container. The longitudinal axis of the sample container receptacle introduced into the rotary head receiving unit or the longitudinal axis of the sample container introduced into the rotary head receiving unit is oriented perpendicular to the axis of rotation of the rotary head or at an angle between more than 0° and less than 90° relative to the axis of rotation. At least one connection region is provided on the rotor to which at least one damping mass can be selectively attached either in a releasable manner or, by means of a fixing element, in a permanent manner for operation. This allows one or plural suitable damping masses to be chosen and attached as required. This makes it possible to minimize the adverse effects of imbalances occurring in operation of the overall dual centrifuge. This in turn results in improved operational safety and a longer service life of the centrifuge. 
     In accordance with an advantageous further development of the invention, the main axis of the dual centrifuge and the axis of rotation of the rotary unit intersect, defining a plane between them in which the axis of rotation intersects the main axis at an angle which is more than 0° and less than 90°. 
     In one embodiment, two equally designed rotary units are provided in a rotor for a dual centrifuge, which units are identically aligned relative to the main axis at a zero position. All the rotary head receiving units, preferably with the sample container receptacles and/or the sample containers, are arranged in an identical manner in the rotary units and the rotary units move synchronously in operation. In this case, the drive axis—main axis—of the centrifuge is the mirror axis of the rotary units. The identical arrangement of the rotary head receiving units, in particular with the sample container receptacles and/or the sample containers, and the synchronous movements of the rotary units prevents the occurrence of imbalances throughout the entire centrifuge. In this case it is advantageous if at least one connection region is also provided on the rotor which region can be used for selectively attaching at least one damping mass thereto either in a releasable manner or, by means of a fixing element, in a permanent manner for operation. 
     It is advantageous if at least one damping mass is provided on the rotor in the connection region. This considerably reduces the adverse effect of the system&#39;s inherent imbalance on the overall system. 
     If the damping mass of a connection region consists of plural mass elements, the imbalance can be counteracted in even more specific manner. In other words, it is possible to create an optimum solution with an as high as possible damping mass for compensating the imbalances and the overall mass of the rotor which latter, however, should not be too high in view of the required rotor acceleration and the existing motor mount. In the case of lower rotor weights, the safety vessel of the centrifuge can be of a weaker design, for example. 
     In one aspect of the invention, a set of mass elements of different weights is provided, which mass elements are used to create a damping mass of a predetermined weight or a plurality of damping masses of predetermined weights which are either identical and/or non-identical, as required. This allows a particularly specific selection of the damping mass for the most varied requirements such as non-uniform loading of the centrifuge with samples or varying size of the mass moved by the rotary head receiving unit with the sample container receptacle and/or the sample container(s). 
     Instead of compiling the damping mass from different mass elements as required, it is also possible to provide a set of damping masses of different and/or identical weights right from the start. As required, a single damping mass will be introduced into the connection region or plural damping masses will be introduced into connection regions. This will enable the centrifuge operator to quickly select and attach the suitable damping mass required for the respective application. 
     In another advantageous embodiment, at least one sample container receptacle or sample container can be mounted in the rotary head receiving unit, and the damping masses are determined as a function of an overall mass of a sample container charged with samples and introduced into the sample container receptacle and the sample container receptacle and/or as a function of an overall mass of a sample container charged with samples and the mass of the rotary unit. This ensures accurate compensation of those masses that might cause an imbalance. As a result, centrifuge operation will be even smoother and safer. 
     It is considered rather advantageous if the sum of the one or plural damping mass(es) attached to the rotor is at a ratio of at least 0.5:1, in particular 1:1, relative to the overall mass which consists of the mass of the sample loads, the sample containers, the sample container receptacles, the rotary head receiving unit and the rotary unit. At these ratios, sufficient damping mass is provided for effectively counteracting imbalances that cannot be compensated completely by synchronizing the orientation of the sample containers, without overloading the centrifuge. 
     In another advantageous embodiment of the invention, the additional rotary mechanism is designed such that a first gear which is stationary with respect to the motor shaft and a second gear which is connected to the rotary head are provided, which motor shaft drives the rotor and, through the rotary movement of the rotor relative to the stationary first gear, also drives the second gear which is operatively connected to the first gear—which then causes the rotary head to be moved. This design of the rotary mechanism ensures that the individual rotary heads are driven in a particularly uniform manner, which results in equally uniform rotation of the individual sample containers. 
     In another embodiment of the invention it has proven advantageous to provide plural rotary units. If the transmission of the rotary movement from the first gear to a second gear each, and thus to the respective rotary head of the rotary unit, is of a design in which all the rotary heads of the rotary units have an identically shaped gear and therefore perform the same angular movement, this will ensure synchronous movement of all the rotary units. 
     In one aspect of the invention, the rotary heads and thus the rotary head receiving units with the sample receptacles and/or the sample containers have a zero position relative to the rotor, at which position intersection points are obtained of the radial line perpendicular to the axis of rotation of the rotary units through the zero position and a radially extending line perpendicular to the main axis of the rotor. This will only allow the sample containers to be introduced into the rotary head receiving unit in a single alignment with the rotary head receiving unit. All the intersection points lie on a circle around the main axis. This arrangement makes it easy to synchronize the rotary heads since it not only predetermines the actual rotary movement, but also the starting points of the rotary movement relative to each other. 
     All the rotary head receiving units and all the sample containers with samples directly or indirectly accommodated therein will preferably be identically oriented relative to the rotor at the zero positions of the rotary heads. In this case, in particular one lid each of the sample container is disposed radially outwardly relative to the rotor. This further enhances the synchronization of the rotary heads. 
     If the sum of the teeth of the engaging second gears of the rotary heads is an integral multiple of the number of teeth of the first gear, it will be easier to maintain constantly uniform angles between the rotary heads on the one hand and the rotor on the other. 
     Higher flexibility with regard to the ratio of the main speed of the dual centrifuge and the speed of the rotary units is achieved by connecting a transmitting gear between the first and second gears, with all of said transmitting gears being of identical design. Changing the respective transmitting gear is a convenient way of achieving a changed gear ratio. 
     To facilitate manual adjustment of the dual centrifuge regarding the positions of the rotary heads prior to starting operation of the centrifuge, it is advantageous to mark the zero position of the rotary head with an optical identifier. This will enable the user to recognize at first glance how the rotary heads will need to be oriented for a synchronous movement. 
     In another advantageous embodiment of the invention, each rotary head has a first bore at the zero position which bore extends through the second gear and will be aligned at the zero position with an associated second bore in a part which is stationary with respect to the rotor. At the zero position of the rotary unit, a pin can then be introduced into the first and second bores to lock the rotary unit at the zero position and prevent it from being rotated out of the zero position. This will align the rotary heads even more precisely than would be possible through a mere visual check. Furthermore, this will also prevent any unintentional rotation when the rotor is being mounted in the centrifuge. As a result, operational safety will be improved. 
     To facilitate the orientation of the rotary units even further and to make operation even safer, the pins associated with the bores can be interconnected via a clip in such a manner that the position of the pins will ensure that the weight distribution of two rotary units is aligned symmetrically relative to one another. This allows the alignment of all rotary heads to be secured in a single manual step. 
     In yet another advantageous embodiment the pin and/or the clip are provided with a blocking device which, in the mounted condition of the pin and/or the clip, will prevent closing of the centrifuge lid. This can be achieved by using especially long pins or a clip that opens particularly wide, for example. This will prevent the centrifuge from being started with the rotary heads still secured in their respective zero positions which would damage the device. 
     As an alternative, the bore and pin can also be arranged the other way round, i.e. with the pin on the rotary head and an associated bore in the clip. 
     The precision of the orientation of the rotary heads is considerably improved by the fact that the zero position has a maximum clearance of 2.5° in the direction of rotation. 
     In accordance with an embodiment of the invention, the rotary heads are coupled to each other via another rotary mechanism in such a manner that the rotary heads of different rotary units are always at a defined angular position relative to each other. This considerably reduces the risk of losing synchronization of the movement of the rotary heads during centrifuge operation. 
     Additional advantages, features and potential applications of the present invention may be gathered from the description which follows in combination with the embodiments illustrated in the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Throughout the description, the claims and the drawings those terms and associated reference signs are used as are listed in the List of Reference Signs below. In the drawings, 
         FIG. 1  is a perspective view of a rotor according to the invention; 
         FIG. 2  is a top view of the rotor of  FIG. 1 ; 
         FIG. 3  is a lateral sectional view of the rotor of  FIG. 1 ; 
         FIG. 4  is a perspective bottom view of an embodiment according to the invention of a rotary unit; 
         FIG. 4 a    is a view of the pin according to the invention; 
         FIG. 5  is a top view of the rotary unit illustrated in  FIG. 4 ; 
         FIG. 6  is a view of a clip according to the invention; 
         FIG. 7  a perspective view of an embodiment according to the invention of a rotary head receiving unit; 
         FIG. 8 a    a perspective view of an embodiment according to the invention of a sample container receptacle which can be disposed in the rotary head receiving unit illustrated in  FIG. 7 , and 
         FIG. 8 b    a perspective view of another embodiment according to the invention of a sample container receptacle which can be disposed in the rotary head receiving unit illustrated in  FIG. 7 . 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  is a perspective view of a rotor according to the invention  10  as part of a symmetric centrifuge with two rotary units  26  for use in a dual centrifuge not illustrated in the figures.  FIG. 2  is a top view and  FIG. 3  is a lateral sectional view, resp., of the rotor illustrated in  FIG. 1 . 
     The rotor  10  has a rotor head  12  of a rotationally symmetric basic shape which defines an envelope. The rotor head  12  is provided with a bottom  14  and a wall  18  that extends upwards and surrounds the bottom  14 . A drive axis A extends perpendicular into the center  16  of the rotor head  12 . A drive shaft not shown in the drawings has its free end extending through the rotor head  12  via an aperture  20  in the bottom  14 , which aperture  20  is concentric with the drive axis A. Above the aperture  20 , a receiving tube  22  is integrally formed with the bottom  14 , which tube  22  serves to center and vertically fix the rotor head  12  in position on the drive shaft. 
     The wall  18  has a vertical portion  18   a  and a portion  18   b  that inclines downwards in the direction of the drive axis. Two apertures  24  are provided that are disposed opposite each other relative to the drive axis A, which apertures  24  partially extend through the vertical portion  18   a  of the wall  18  and the inclined portion  18   b  of the wall  18 . 
     The rotary units  26  each have an axis of rotation R 1 , R 2  and are oriented by way of the apertures  24  in such a way that the axes of rotation R 1  and R 2  intersect the drive axis A at an acute angle above the rotor  10 . Furthermore, the free ends of the rotary units  26  facing away from the drive axis A, i.e. the housings  28  described in the following, see  FIG. 4 , protrude from the envelope in the area of the inclined portion  18   b  of the wall  18 . 
     Each rotary unit  26  has a largely rotationally symmetric outer contour and comprises a rotatably mounted rotary head  30 , see  FIG. 3 , for supporting a rotary head receiving unit  80  with a sample container receptacle  100 ,  110  inserted therein, which latter contains sample containers for samples to be centrifuged, and a housing  28  with a bearing  32  for the rotary head  30 , which bearing  32  is in turn engaged by a bearing shaft of the rotary head  30 , which bearing shaft (not shown for reasons of clarity) is disposed on the side of the rotary head  30  which faces the housing  28 . 
     The rotary head  30  has an outer wall  34  which is mounted concentrically with the rotational axis R 1 , R 2 . The housing  28  is provided with a wall  38  that is concentric with the rotational axis R 1 , R 2 . The diameter of the rotary head  30  is larger than that of the housing  28  which results in the formation of a shoulder  36  between the outer wall  34  of the rotary head  30  and the wall  38  of the housing  28 , with the rotary unit  26  partially engaging in the associated aperture  24  via this shoulder  36 , see  FIG. 1 . 
     The dimensions of the housing  28  have been adapted to the respective associated areas of the apertures  24 . For ensuring that the housing  28  and the rotor head  12  are non-rotatably mounted, a groove is provided in the housing  28  parallel to the axis of rotation R 1 , R 2  and a projection associated with said groove is provided on the rotary head  12 . Both the groove and the projection have been omitted from the drawings for reasons of clarity. Moreover, the groove and the projection can also be disposed the other way round. Furthermore, it is also possible to choose a polygonal design for the housing  28  instead of a cylindrical shape so as to mount a housing in a rotary head in a non-rotatable manner. 
     As seen in  FIG. 1 , the side of the rotary head  30  which is remote from the housing  28  is furthermore closed by a closure lid  40  which is disposed concentrically with the rotational axes R 1 , R 2 . Equally concentrically mounted on the closure lid  40  is a closure knob  42  which serves as a handle for unlocking the closure lid  40  by means of a rotary movement and taking it off or for putting the closure lid  40  on the rotary head  30  and locking it in place by means of a rotary movement in a direction opposite to the locking direction. 
     A circumferential projection  44  is provided on the outer wall  34  adjacent to the shoulder  36 , as seen e.g. in  FIG. 4 , which projection  44  fixes a gearing  46  concentrically relative to the axes of rotation R 1 , R 2 , which gearing  46  is non-rotatably connected to the outer wall  34 . For transmitting the rotary movement of the rotary heads  30  about the axes of rotation R 1 , R 2  of the rotary units  26 , a central gear (omitted from the figures for reasons of clarity) is provided below the rotor head  12 , which central gear is non-rotatably connected to the rotatable rotor head  12 , e.g. by means of a screwed connection to a motor housing (not shown in the figures). A transmitting gear can be provided between said gearing  46  and said central gear so as to achieve different gear ratios. The transmission of rotary movements in such a manner is well known and has already been described in the prior art, for which reason no further explanations are necessary here. 
     The ratio of the main rotation (rotation of the rotor  10 ) to the reverse rotation (rotation of the rotary head  30 ) is defined by the gear ratio between the gear  46  and the central gear (not shown) and, if necessary, an additional transmitting gear. Once the rotor head  12  has been removed, the transmitting gear (not shown) and the central gear can be easily exchanged. This allows the speed ratio to be changed in a simple manner by adapting the respective diameters of the gear (not shown) and the central gear. 
     On the side of the housing  28  which is remote from the rotary head  30 , cooling ribs  50  are provided. The cooling ribs  50  are aligned perpendicular to the direction of rotation of the rotor head  12 . 
     The side of the wall  18  which faces the center  16  of the rotor head  12  is formed as a connection region  52  on which two disk-shaped damping masses  54  are disposed opposite each other relative to the center  16  of the rotor head  12 . The damping masses  54  are provided to reduce the adverse effects of imbalances which may occur during operation, in particular in the rotary units  26 . 
       FIG. 4  is a perspective bottom view of the rotary unit  26  illustrated in  FIGS. 1 through 3  with the closure lid  40  removed. This view clearly shows the arrangement in particular of the projection  44  and the gearing  46  on the outer wall of the rotary head  30  as well as of the cooling ribs  50  on the side of the housing  28  which faces away from the rotary head  30 . 
       FIG. 5  is a top view of the rotary unit  26  illustrated in  FIG. 4 . A bottom  60  which has a circular area and a center  62 , and an inner wall  58  provided on the periphery of said bottom  60  and extending concentrically with the outer wall  34  of the rotary head  30  delimit a receiving area  56  which is open towards the top and adapted to receive a rotary head receiving unit  80  described below with reference to  FIG. 7 . 
     In the bottom  60 , ten uniformly spaced bores are provided on a circular line K 2  extending around the center  62  for reasons of clarity, which bores are used for riveting the rotary head  30  to the housing  28  to form a structural unit. 
     On another circular line K 2  which likewise extends around the center  62 , eight uniformly spaced recesses  66  are provided. When the rotary head receiving unit  80  as exemplarily illustrated in  FIG. 7  is inserted, the recesses  66  serve to accommodate wedges, pins or the like provided on the rotary head receiving unit  80  as guiding means and for improving the safety of the connection. A lateral guide (not shown) for which an associated counter-guide is provided on the outer wall ensures that the rotary head receiving unit  80  can be mounted in the rotary unit in a single orientation only. 
     Furthermore, adjacent to the inner wall  58 , a bore  68  is provided in the bottom  60 . As can also be seen in  FIG. 4 , this bore  68  extends completely through the bottom  60  and serves to accommodate a pin  70  as shown in  FIG. 4 a   . At the same time, the bore  68  indicates a zero position N of the rotary unit  26  which can be used to align the rotary unit  26  in such a way that it moves in synchronization with other rotary units  26  disposed in the rotor head  12 . Diametrically opposite said bore  68  another bore may be provided for the sake of symmetry, thus compensating for any imbalance caused by the bore  68 . 
     At the end of the pin  70  there is a ball-shaped grip  71  and the length of the pin is dimensioned such that it extends through the bore  68  and that its free end will engage in a bore provided in the rotor head  12 , which latter bore has been omitted from the drawings for reasons of clarity. This fixes the rotary unit  26  at the zero position N. Moreover, the pin can be dimensioned such that it will prevent closing of a centrifuge lid. 
       FIG. 6  shows a clip  72  which can be used to fix two rotary units  26  at their respective zero position N at the same time. A pin  74  each is provided on either free end of the clip  72 . The two pins  74  are of the same length as the pin  70  and are spaced from each other via a resiliently elastic connecting clip  76  and are arranged at an angle from each other such that they can be introduced simultaneously into two bores  68  of two rotary heads  30 . The resiliently elastic design of the connecting clip  76  allows minor changes of the distance and the setting angle as may be required for insertion and removal of the pins  74 . 
     At the center of the connecting clip  76  a ball-shaped grip  78  is provided. This grip  78  first of all facilitates handling of the clip  72  and secondly, in the inserted condition of the clip  72 , the grip  78  will be positioned so as to prevent complete closure of a centrifuge lid. 
       FIG. 7  is a view of an embodiment of a rotary head receiving unit  80  which can be mounted in the receiving area  56  of the rotary head  30  so as to support the sample container receptacles  100  and  110  exemplarily shown in  FIGS. 8 a  and 8 b    safely therein. The outer circumference of the rotary head receiving unit  80  has been adapted to the receiving area  56 . 
     The rotary head receiving unit  80  has a safety wall  82  and a bottom  84 . An inner contour  86  of the safety wall  82  and the bottom  84  delimit a cross-shaped receiving space  88  which is open towards the top. Two rectangular legs  88   a  and  88   b  of the receiving space  88  are disposed perpendicular to each other, with the base area each of the first leg  86   a  and of the second leg  86   b  being identical and corresponding to the base area of the sample container receptacles  100 ,  110  illustrated in  FIGS. 8 a  and 8 b   , resp. 
     The first leg  88   a  serves to accommodate the sample container receptacle  100 . For this purpose, a recess  90  is provided in the safety wall  82  at either end of the leg  88   a , which two recesses  90  are arranged diametrically to one another relative to the leg  88   a . The recesses  90  serve to reliably clamp the sample container receptacle  100  with the centrifuge tubes inserted therein in the rotary head receiving unit  80 , as will be explained in more detail with reference to  FIG. 8   a.    
     The second leg  88   b  serves to receive the sample container receptacle  110 . For this purpose, one recess  92  is provided in the safety wall  82  at one end of the leg  88   b  and two recesses  94  are provided in the safety wall  82  at the second end of the leg  88   b . The recesses  92 ,  94  are used to safely clamp the sample container receptacle  110  in the rotary head receiving unit  80 , as will be explained in more detail with reference to  FIG. 8   b.    
       FIG. 8 a    is a view of a first sample container receptacle  100  according to the invention, which, as described with reference to  FIG. 7 , is adapted to be received in the first leg  88   a  of the rotary head receiving unit  80 . 
     The sample container receiving area  100  has an aperture  104  each in two front faces  102 , which aperture  104  will accommodate and vertically support therein a centrifuge tube as a sample container, which centrifuge tube has been omitted from the drawing for reasons of clarity. On either front face  102  an end of a centrifuge tube (lid side) protruding from the respective aperture  104  engages in an associated recess  90  in the safety wall  82 . This clamps the sample container receptacle  100  in position in the rotary head receiving unit  80 . 
       FIG. 8 b    is a view of a second sample container receptacle  110  which is adapted to be received in the second leg  88   b  of the rotary head receiving unit  80 . 
     In  FIG. 8 b   , on its front face  112  facing the observer, the sample container receptacle  110  has an aperture  114 , and on its front face  112  facing away from the observer, it has two apertures  114 . These apertures  114  can be used to receive and vertically support centrifuge tubes therein, which tubes have been omitted from this figure for reasons of clarity. Similar to the solution illustrated in  FIG. 8 a   , here, too, the ends of a centrifuge tube which protrude from the respective aperture  114  on either front face  112  engage in an associated recess  92 ,  94  in the safety wall  82 . This clamps the sample container receptacle  110  in position in the rotary head receiving unit  80 . 
     The rotary head receiving unit  80  and the sample container receptacles  100  and  110  were chosen as an example, since arranging elongated sample container receptacles with sample containers perpendicular to the axis of rotation R 1 , R 2  of the rotary unit  26  entails a high risk of causing imbalances, for which reason attaching a damping mass is considered particularly advantageous. However, there are numerous other examples of how sample container receptacles for sample containers can be mounted in a different manner, also mounting the sample container directly in the rotary head receiving unit. 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               10  rotor 
               12  rotor head 
               14  bottom 
               16  center 
               18  wall 
               18   a  vertical portion 
               18   b  inclined portion 
               20  aperture 
               22  receiving tube 
               24  aperture 
               26  rotary unit 
               28  housing 
               30  rotary head 
               32  bearing 
               34  outer wall 
               36  shoulder 
               38  wall 
               40  closure lid 
               42  closure knob 
               44  projection 
               46  gearing 
               50  cooling ribs 
               52  connection region 
               54  damping masses 
               56  receiving area 
               58  inner wall 
               60  bottom 
               62  center 
               64  bores 
               66  recesses 
               68  bore 
               70  pin 
               71  grip 
               72  clip 
               74  pins 
               76  connecting clip 
               78  grip 
               80  rotary head receiving unit 
               82  safety wall 
               84  bottom 
               86  inner contour 
               88  receiving space 
               88   a  first leg 
               88   b  second leg 
               90  recess 
               92  recess 
               94  recess 
               100  sample container receptacle 
               102  front face 
               104  aperture 
               110  sample container receptacle 
               112  front face 
               114  aperture 
             A drive axis 
             R 1 , R 2  axes of rotation 
             K 1  circular line 
             K 2  circular line 
             N zero position