Patent Publication Number: US-2023149618-A1

Title: Insert for a centrifuge rotor

Description:
The present application is a National Stage application of PCT International Application No. PCT/EP2021/058069, filed on Mar. 29, 2021, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     The invention relates to an insert for a rotor, which can be rotated about a rotor axis, of a centrifuge, said insert being of the type specified in the preamble of claim  1 . 
     Such inserts for centrifuge rotors have been known for some time and are used for the automated separation as well as the separation integrated within the centrifuge, of for example red blood cells from blood plasma in a process bag of a blood bag system. A process bag of a blood bag system filled with donor blood is used in such an insert, for example. The process bag contains the pre-filtered blood donation, for example. The blood bag system has one or more satellite bags, for example, that may be empty or pre-filled with a culture medium. The satellite bags and the process bag are connected to one another via plastic tubings. During centrifugation, the red blood cells—RBC—and the blood plasma—PPP—settle on the outer rim according to their respective density. Sedimentation takes place at 2,500 rpm (revolutions per minute) of the centrifuge rotor, so that the red blood cells, which are denser, will accumulate towards the outside of the interior of the process bag, and the less dense blood plasma will settle further inside. 
     The insert is provided with a housing comprising a process container for the process bag as part of the housing and further containers for the satellite bags. A slider is arranged in the container for the process bag, which slider is adapted to be extended radially, with respect to a rotor axis, against the process bag and retracted again. For this purpose, the slider is connected to a drive that cooperates with a rotatable spindle nut and a spindle. The spindle nut is rotatably mounted in the housing of the insert. The spindle passes through the spindle nut, is translationally slidably mounted in the spindle nut and is non-rotatably connected to the slider. 
     As has been explained, the slider is mounted in the process container and acts on the process bag in a predetermined manner, in that the spindle, and thus via it the slider, is moved between a starting position and an operating position in the direction toward and away from the rotor axis. The spindle nut is rotatably mounted in the housing of the insert via at least one bearing and serves as a means to convert the rotational motion initiated by the drive into a translational motion. 
     Since heat is generated during centrifugation, which, however, has a detrimental effect on the red blood cells and blood plasma since blood cells and blood plasma may become unusable, the rotor chamber of the centrifuge, in which the rotor with the insert(s) is located, is cooled. Cooling of the rotor chamber is therefore intended to prevent the red blood cells and blood plasma from heating up by all means. 
     For separating the blood plasma from the red blood cells, the slider is pressed against the process bag via the spindle at a low centrifuge speed, for example in the 300 rpm to 600 rpm range, and thereby displaces the blood plasma in the process bag from it. Via the connected plastic tubing, which is held in place in particular in and on the insert by integrated tube clamps, together with an optical detection system, the blood plasma is thus pressed into the one or plural associated satellite bag(s). The red blood cells then remain in the process bag, for example. This pressing process by moving the slider onto the process bag takes place under the effect of centrifugal force, i.e. during operation of the centrifuge, among other things in order to stabilize the individual layers in the process bag. 
     The problem with the inserts known from the prior art is that the process bags, but also the satellite bags, can become contaminated, especially by the moving parts of the insert, for example by abrasion or rust produced during operation and/or by lubricants, with the result that only part of the blood plasma and of the red blood cells is still usable, or they become unusable in their entirety. Rust may be caused by the cooling and the associated condensation of the air in the rotor chamber. Lubricant and abrasion can come from the parts moving relative to each other and may deposit on the bag system as a result of centrifugal forces. As a result of diffusion processes through the bags, the blood samples, blood cells and blood plasma may become contaminated. 
     It is the object of the invention to improve on an insert for a rotor of a centrifuge of the type specified in the preamble term of claim  1  in such a way that contamination of the bags of the bag system, i.e. the process bags and possibly the satellite bags, can almost completely be eliminated. 
     This object is accomplished by the characterizing features of claim  1  in conjunction with the features of its preamble. 
     The dependent claims relate to advantageous further embodiments of the invention. 
     The invention is based on the insight that the bearing for the slider is a major source of potential contamination within the insert and bag system, for which reason measures to limit contamination must start here. It has been shown that contamination can be significantly reduced, in particular by using a lubricant-free bearing. 
     According to the invention, the bearing is therefore constituted by a lubricant-free bearing having an outer bearing ring in contact with the housing and a bearing ring in contact with the spindle nut. This is a simple way to prevent lubricant from escaping and contaminating the bags of the bag system. 
     In addition, in order to avoid contamination by rust in particular, a stainless bearing is used. Consequently, condensation will no longer have any influence on rust formation in the bearing. 
     However, since the spindle nut in the bearing moves during centrifugation to press the blood plasma into the satellite bags, the bearing must additionally withstand the forces that occur during centrifugation. It is therefore advantageous for the bearing to be constituted by a rolling bearing which is capable of absorbing higher forces. 
     However, the problem with rolling bearings is that they cause abrasion. In one embodiment of the invention, the bearing is therefore formed by a hybrid bearing. Hybrid bearings are almost completely abrasion-free. The rolling elements can be made of ceramic, and the outer ring and inner ring can be made of stainless steel. 
     In order to also protect the bag system and the rest of the insert from minor abrasion, the bearing is formed by a sealed, encapsulated, in particular a plastic-encapsulated, rolling bearing. 
     The outer ring and/or the inner ring of the rolling bearing can be of a single-part or a multi-part design. For the centrifugal forces acting in the centrifuge, it is advantageous, with regard to bearing stability, for the outer ring and/or the inner ring of the rolling bearing to be formed in one piece. 
     Especially when only one bearing is used, it is considered favorable for the bearing to be designed as a four-point bearing. Four-point bearings are, for example, single-row radial angular contact ball bearings whose raceways are designed to support axial loads in both directions. Radial loads can only be absorbed up to a fraction of the axial load. 
     Preferably, the bearing has nine rolling elements. 
     In one embodiment of the invention, the axis of rotation of the bearing is on a radial line of the rotor axis. In this way, any potential imbalances are avoided during the process. 
     To further limit the spread of rust, abrasion and the like, some areas of the bearing are enclosed by the housing, the spindle nut, a clamping element, a fixing plate and another seal. 
     In one embodiment of the invention, an outer seal is fitted to the bearing on the side of the bearing facing away from the rotor axis, which seal acts to seal a bearing gap between the housing and the spindle nut. The seal prevents contaminated substances from escaping through the outer seal. 
     Preferably, the housing is provided with a wall on which the bearing is arranged. In addition, the drive has a motor and a first gear unit connected to the motor. The motor and the first gear unit are located on the one side of the wall, and the slider is located on the other side of the wall. The wall can be used as an easy means to separate the slider acting on the bag system from most of the moving parts. In addition, the wall serves to receive the outer ring of the bearing and can form the rear wall of the container. 
     In order to transmit the drive force from the motor to the spindle nut via the first gear unit, the drive has a second gear unit which is connected to both the first gear unit and to the spindle nut, the second gear unit being located on the same side as the slider. 
     The drive can be arranged closer to the rotor axis than the slider. This is also favorable in that the moving masses are then closer to the rotor axis, resulting in more stable running of the centrifuge. 
     The wall may have a shoulder for accommodating the bearing. In this case, the bearing is inserted into the shoulder with the outer ring of the bearing from the side that is closer to the rotor axis. This ensures that there is already a separation between the bearing on the one side and the slider in the container for the blood bag system on the other side. 
     The spindle nut may have a shoulder to receive the bearing. In this case, the bearing is inserted into the shoulder with the inner ring of the bearing from the side that is closer to the rotor axis. Installation is thus carried out from the side of the wall facing away from the slider. This is a simple way of structurally separating the moving parts of the drive with the bearing on the one side from the slider on the other side. 
     Preferably, on the side of the housing remote from the shoulder of the wall, the outer ring is connected to the wall of the housing in the axial direction by a fixing element, in particular a fixing plate, which is connected to the wall of the housing, in particular in a releasable manner. 
     The inner ring can be connected to the spindle nut in the axial direction on the side remote from the shoulder of the spindle nut by a clamping element, in particular by a clamping ring mounted on the spindle nut or a threaded nut mounted on the spindle nut. 
     In addition, an inner seal can be provided between the fixing element and the clamping element in order to seal the bearing gap between the fixing plate and the clamping nut. This allows further separation of contaminating substances from the container with the slider in a simple way. 
     Additional advantages, features and possible applications of the present invention will be apparent from the description which follows, in which reference is made to the embodiments illustrated in the drawings. 
    
    
     
       Throughout the description, the claims and the drawings, those terms and associated reference signs are used as are stated in the list of reference signs below. In the drawings, 
         FIG.  1    is a perspective view, as seen at an angle from above, of a centrifuge with its lid open and having inserts according to the invention installed in the rotor; 
         FIG.  2    is a perspective detail view, as seen at an angle from above, of the inserts of  FIG.  1    installed in the rotor; 
         FIG.  3    is a perspective view of an insert that has been removed from the rotor; 
         FIG.  4    is a perspective view of the insert of  FIG.  3    with a partial section through the inner area of the insert in the area of the inner cover; 
         FIG.  5    is a perspective view of the insert of  FIG.  3    without an inner cover and with other internals; 
         FIG.  6    is a side sectional view through the insert along an axis of rotation of a spindle nut of the insert, showing a slider in its retracted state and a process bag inserted into a container, and 
         FIG.  7    is a side sectional view similar to that of  FIG.  6   , but with the slider in its extended state. 
     
    
    
     Illustrated in  FIGS.  1  to  7    is an embodiment of an insert  10  fora rotor  14 , which can be rotated about a rotor axis  12 , of a centrifuge  16 . 
     As can be seen from  FIG.  1   , the centrifuge  16  is provided with a closed housing  18  which has a circular loading opening  22  in its top ceiling wall  20 . The loading opening  22  may be closed by a cover  24  hinged to the housing  18 . For this purpose, the cover  24  has a sealing ring  22   a  adapted to the loading opening  22  and arranged in alignment with this loading opening  22 . When the cover  24  is closed, the sealing ring  22   a  engages an annular shoulder  26  of the loading opening  22  and tightly closes the loading opening  22  in this way. 
     When the lid  24  is open, the loading opening  22  allows loading of the rotor  14 , which has six inserts  10   a  to  10   f  according to the invention installed in it, see  FIG.  2   . The rotor  14  with the inserts  10  is arranged in a cooled rotor chamber  28 . All six inserts  10   a  to  10   f  are of the same structure, so that the description of one insert  10  applies to all inserts  10   a  to  10   f.    
     As can be seen from  FIGS.  3  to  7   , an insert  10  includes a housing  30 . The housing  30  is provided with an outer wall  32  and an inner cover  34 , which delimit the housing radially outwardly and inwardly, respectively. In addition, the housing  30  includes a process container  36  that is closed by a process container lid  38  with a handle  40 . In the upper portion of the process container  36 , the process container lid  38  is connected to an upper insert wall  46  of the housing  30  of the insert  10  by first and second joints  42 ,  44 . 
     Adjacent to a rear wall  48  of the process container  36  is a supporting wall  50  which is screw-connected to the side of the housing  30  in the area of the rear wall  48  of the process container  36 , see  FIG.  4    and  FIG.  5   . The rear wall  48  and the supporting wall  50  may also be identical, as shown in  FIGS.  6  and  7   . 
     A motor  52  and a first gear unit  54  are fixed to the supporting wall  50 . A drive spindle (not shown here) extends through an opening  56 , see  FIG.  4   , and connects the first gear unit  54  with a second gear unit  58 , see  FIGS.  6  and  7   . The second gear unit  58  is connected to a spindle nut  62  which is mounted so as to be rotatable in a bearing  60  in the supporting wall  50 , thus allowing the spindle nut  62  to be driven via the motor  52 , the first gear unit  54  of the drive spindle (not shown here) and the second gear unit  58 . 
     An axially displaceable spindle  64  is mounted in the spindle nut  62 , which has a thread  64   a  on its outside in which an internal thread  62   a  of the spindle nut  62  engages. The spindle  64  is non-rotatably connected to a slider  66 . Rotation of the spindle nut  62  causes the spindle, and thus also the slider  66 , to be axially displaced via the engaging internal thread  62   a  of the spindle nut  62  and the external thread  64   a  of the spindle  64 . Depending on the direction of rotation, there is an axial displacement of the spindle  64  away from or towards the rotor axis  12 . The axis of rotation of the spindle nut  62  and the longitudinal axis of the spindle  64  form a common axis  68 , which extends radially away from the rotor axis  12 . 
     The spindle nut  62 , in cooperation with the spindle  64 , thus serves as a motion converter for converting a rotational motion introduced into the spindle nut  62  by the motor  52 , the first gear unit  54 , and the second gear unit  58  into a translational motion of the spindle  64  and thus of the slider  66 . 
     The spindle  64  protrudes far into the space delimited by the inner cover  34  and thus projects from the spindle nut  62  because the slider  66  is in its starting position, see  FIG.  4   ,  FIG.  5    and  FIG.  6   . 
     The bearing  60  is a lubricant-free, stainless steel rolling bearing, namely a four-point hybrid bearing. The bearing  60  has its outer ring  60   a  abutting a shoulder  70  of the supporting wall  50 . The outer ring  60   a  is fixed without play in the axial direction in the shoulder  70  by a fixing plate  72  fixed to the supporting wall  50  on the side facing away from the process container  36 . Furthermore, the bearing  60  has its inner ring  60   b  resting against an outer shoulder  74  of the spindle nut  62 . A clamping ring  76  is used to firmly clamp the inner ring  60   b  in the direction of the outer shoulder  74 . 
     In the views of  FIG.  6    and  FIG.  7   , a split inner ring  60   b  was used for the bearing  60 . However, it is more convenient to use a single-piece inner ring  60   b.    
     Mounted between the outer ring  60   a  and the inner ring  60   b  are nine rolling elements in the form of rolling balls  60   c . The bearing  60  is terminated with a bearing housing  60   d  disposed to the left and right of the rolling balls  60   c  and between the outer ring  60   a  and the inner ring  60   b . The bearing housing  60   d  is made of plastic and seals the bearing  60  so that no abrasion can escape to the outside. 
     The outer ring  60   a  and the inner ring  60   b  are made of stainless steel, in particular X1005CrMo17. The rolling balls  60   c  are made of ceramic, in particular Si3N4. 
     As can be seen in particular from  FIG.  6    and  FIG.  7   , a bearing gap  78  located in the region of the shoulder  70  of the supporting wall  50  is sealed by an outer seal  80 . In this way, the encapsulated bearing  60  is further enclosed/encapsulated by the supporting wall  50 , the outer seal  80 , the spindle nut  62 , as well as the clamping ring  76  and the fixing plate  72 . 
     Furthermore, an additional seal  82  may also be provided between the fixing plate  72 , the clamping ring  76  and the inner ring  60   b.    
     The shoulder  70  of the supporting wall  50  and the outer shoulder  74  of the spindle nut  62  are arranged so that the bearing  60  is mounted from the side of the supporting wall  50  that is closest to the rotor axis  12 . The spindle nut  62 , on the other hand, is inserted from the side of the supporting wall  50  and the rear wall  48  of the process container  36  into an associated opening  84 , which is remote from the rotor axis  12 . 
     The inner cover  34  is placed on the supporting wall  50  from the side of the supporting wall  50  that faces the rotor axis  12  and is releasably connected to it by means of a click mechanism (not shown in more detail here). 
     As seen in  FIGS.  6  and  7   , a process bag  86  of a bag system has each been placed in the process container  36 . This process bag  86  is filled with donor blood.  FIG.  6    shows the slider  66  in its starting position. Plastic tubing  88  connects the process bag  86  to satellite bags (not shown here). In this starting position of the slider  66 , centrifugation starts by rotating the rotor  14 . This process causes the red blood cells—RBC—and the blood plasma—PPP—to deposit on the outer edge according to their respective density. Sedimentation takes place at a speed of 2,500 rpm (revolutions per minute) of the rotor  14  of the centrifuge  16 , causing the red blood cells, which are of higher density to deposit toward the outside inside the process bag  86 , with the blood plasma of lesser density, to be deposited further towards the inside. Once separation is fully completed, the blood plasma is removed from the process bag  86 . 
     For this purpose, the motor  52  is started and drives the spindle nut  62  via the first gear unit  54  and the second gear unit  58 . Subsequently, the spindle  64 , which is connected to the slider  66 , is caused to move translationally from its starting position as shown in  FIG.  6    towards its operating position, and, along with the spindle  64 , so is the slider  66 . 
     In order to move the blood plasma out of the process bag  86  that contains the red blood cells, without, however, entraining the red blood cells, the slider  66  is successively pressed against the process bag  86  via the spindle  64  in the manner described, at a low speed of the centrifuge  16 , for example in the range of between 300 rpm and 600 rpm. This causes the blood plasma in the process bag  86  to be displaced from it. Via the connected plastic tubing  88 , which is held in and on the insert by integrated tube clamps (not shown here), together with an optical detection system which interacts with a controller/control unit, the blood plasma is pressed into the associated one or plural associated satellite bag(s). This ensures that the red blood cells remain in the process bag. This process of pressing the blood plasma into the satellite bag by means of the movement of the slider  66  occurs under the action of centrifugal force, i.e. during operation of the centrifuge  16 , among other things to stabilize the individual layers in the process bag  86 . 
     According to the invention, the bearing  60 , which is a potential source of contaminants, is largely designed such that no contaminants are present in the first place and will not be produced either. In addition, the bearing  60  is enclosed/encapsulated in stages so that, in any event, contaminants are prevented from entering the process container  36  and thus from being introduced into the process bag  86 . Contamination of the substances contained in the process bag  86 , for example blood donations, is thus effectively prevented in a simple manner. 
     LIST OF REFERENCE SIGNS 
     
         
         
           
               10  insert 
               10   a  first insert 
               10   b  second insert 
               10   c  third insert 
               10   d  fourth insert 
               10   e  fifth insert 
               10   f  sixth insert 
               12  rotor axis 
               14  rotor 
               16  centrifuge 
               18  housing 
               20  upper ceiling wall of centrifuge housing 
               22  loading opening 
               22   a  sealing ring 
               24  lid 
               26  annular shoulder 
               28  rotor chamber 
               30  housing of insert  10   
               32  outer wall 
               34  inner cover 
               36  process container 
               38  process container lid 
               40  handle 
               42  first joint 
               44  second joint 
               46  upper insert wall  46  of housing  30  of insert  10   
               48  rear wall of process container  36   
               50  supporting wall 
               56  opening 
               58  second gear unit 
               60  bearing 
               60   a  outer ring of bearing  60   
               60   b  inner ring of bearing  60   
               60   c  rolling elements of bearing  60   
               60   d  bearing housing of bearing  60   
               62  spindle nut 
               62   a  internal thread of spindle nut  62   
               64  spindle 
               64   a  external thread of spindle  64   
               66  slider 
               68  axis 
               70  shoulder of supporting wall  50   
               72  fixing plate 
               74  outer shoulder of spindle nut  62   
               76  clamping ring 
               78  bearing gap 
               80  outer seal 
               82  additional seal, inner seal 
               84  opening for spindle nut in supporting wall  50  and rear wall  48  of process container  36   
               86  process bag 
               88  plastic tubing