Abstract:
The present invention provides a zonal centrifuge which has superior workability and functionality when a sample is filled and extracted. An oil bearing fitted to an outer circumference of a lower tube of a rotor is arranged on an internal face of a bearing housing fixed over a door adapter of the centrifuge. As the oil bearing and the lower tube are lubricated, a vacuum environment in a rotor rotating chamber is maintained. A rotating seal located at an upper leading end of the lower tube of the rotor and a fixing seal facing the rotating seal are arranged and provided in a sealed space formed by a mechanical seal member and the bearing housing, and the fixing seal is so manipulated as to be able to freely join and separate from the rotating seal.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a centrifuge which separates, by centrifugation, fine particles in a liquid sample in which separation-target particles are mixed. 
     2. Description of the Related Art 
     In the fields of biology, medical science, agriculture, and the like, a zonal centrifugation method is used in order to separate fine particles like intracellular materials or viruses. According to the zonal centrifugation method, one which is called a swing rotor (or swinging bucket rotor) and which rotates with a plastic test tube filled with a sample being inserted into a bucket of the rotor is used. 
     A product so-called a zonal rotor is also sold and used instead of the swing rotor. As such a product, a P35ZT-type zonal rotor made by Hitachi Koki, Co., Ltd. is commercially available. The zonal rotor has characteristics such that it has little turbulence of a sample since there is no “wall effect”, has a large capacity, and continuously allows filling of a sample, collection thereof and analytical operation when rotating in comparison with the swing rotor. The zonal rotor is mainly used for separation needing a great capacity and a high precision like vaccine production. An explanation will now be given of a configuration of a conventional centrifuge having the zonal rotor. 
       FIGS. 5A and 5B  are diagrams showing a whole configuration of a conventional centrifugal separation device (hereinafter, “centrifuge”)  51   a  having a zonal rotor (hereinafter, “rotor”)  10 .  FIG. 5A  shows a state when a sample is filled/collected, while  FIG. 5B  shows a state when centrifugal separation is carried out. As shown in  FIG. 5A , the centrifuge  51   a  comprises a driving unit  53 , the rotor  10  and a rotor rotation chamber  55  all arranged inside a casing  52  formed of sheet-metal parts, a control panel  57  indicating a driving state, and, an electrical control unit  60 , a vacuum evacuation device  62 , and a rotor-chamber-interior cooling device  64  which are illustrated with a simplified contour respectively in the figure. 
     The rotor  10  stores a separation-target sample  184  shown in  FIG. 6 , and as the rotor  10  is rotated and driven by the driving unit  53 , the rotor  10  separates the sample  184  in such a way that the sample  184  forms layers in the radial direction. As shown in  FIGS. 5A ,  5 B and  FIG. 6 , the rotor  10  mainly comprises a bowl-like rotor body  12 , partition walls (hereinafter, “septa”)  16   a  arranged in the rotor body  12  and dividing a sample storage chamber  18  into sector forms as viewed from the above, and a cover  14   a  having a female thread fastened with a male thread provided on an upper external face of the rotor body  12 , functioning as a lid, and provided with an opening at the center thereof where a shaft  70   a  passes all the way through. 
     As shown in  FIG. 6 , the shaft  70   a  is formed in a cylindrical shape, and a lower end thereof is fixed to an internal bottom face of the rotor body  12 . An upper end of the shaft  70   a  is attached with a rotating seal (first sealing member)  72  used for taking out/putting in the sample  184 . The shaft  70   a  has a sample passageway  300  and an extrusion liquid passageway  320 . The sample passageway  300  runs from an opening formed in the upper end of the shaft  70   a  to an opening formed in a side face of the shaft  70   a  and located in the interior of the rotor  10 . The extrusion liquid passageway  320  penetrates the septa  16   a  in the radial direction of the rotor  10  from the upper end of the shaft  70   a , and is communicated with a space between the rotor  10  and the septa  16   a.    
     When centrifugal separation is carried out, the rotor  10  is mounted in such a way that a rotation shaft opening  120  shown in  FIG. 6  is connected to a rotation shaft  54  provided upwardly of the driving unit  53  shown in  FIG. 5A . Thereafter, in accordance with the steps and procedures shown in  FIG. 7 , the centrifuge  51   a  is operated. Then, a target is separated by centrifugation and collected. An explanation will be given of operation steps of the rotor  10  with reference to  FIG. 7 . 
     At a step of “filling a sample”, a seal member  76  is attached with the rotor  10  being rotating at about 3000 rpm in an atmosphere. The seal member  76  is caused to contact and slide the rotating seal  72  of the rotor  10  to configure a mechanical seal. Next, using a liquid-feeding pump (not shown), a separation-target sample  184  and a density gradient liquid necessary for separating the sample  184  are filled. The seal member  76  is attached to a seal supporting plate  58  attached in the rotor rotation chamber  55  in such a manner as to be coaxial with a rotation axis of the rotor  10 . Thereafter, the sample  184  is filled into a central part of the rotor  10  through the sample passageway  300  shown in  FIG. 6 , and then a preparation for centrifugal separation is completed. This operation is carried out with a door  56   a  of the centrifuge  51   a  being opened. 
     Next, at a step of “centrifugal separation” shown in  FIG. 7 , the seal member  76  is removed, and a cap  74  is attached to a leading end of the shaft  70   a  shown in  FIG. 6  in order to airtightly sealing the interior of the rotor  10 . The cap  74  is attached to the upper end of the shaft  70   a  while being sealed with an O-ring or the like. When the rotor  10  is rotated at high speed to perform centrifugal separation on the sample  184 , the door  56   a  is closed, the rotor rotation chamber  55  is vacuumed (depressurized) by the vacuum evacuation device  62  shown in  FIG. 5A , so that generation of heats due to friction of the rotor  10  with the air is suppressed. However, when the centrifuge  51   a  is operated under a depressurized condition, the sample  184  in the rotor  10  is likely to be evaporated. The cap  74  is used in order to suppress such evaporation. Next, the rotor rotation chamber  55  is vacuumed, the rotation speed of the rotor  10  is increased to a predetermined rotation speed, and centrifugal separation with a time appropriate for separation of the sample  184  is carried out. 
     After the centrifugal separation, at a step of “collecting the sample” shown in  FIG. 7 , the rotation speed of the rotor  10  is reduced again to 3000 rpm, and the pressure of the rotor rotation chamber  55  is returned back to the atmospheric pressure. Thereafter, the door  56   a  is opened, the cap  74  is removed, the sealing member  76  is attached again, and the separated liquid in the rotor  10  is collected. For example, in the case of sample collection at 3000 rpm, a liquid having a large density (hereinafter, “extrusion liquid”) is fed from an external wall side in the rotor  10  through the extrusion liquid passageway  320  of the shaft  70   a . The sample  184  is ejected to the exterior through the sample passageway  300  of the shaft  70   a , and collected. A density gradient liquid containing settled-out particles can be dividingly collected by a fraction collector while continuously measuring a light absorption degree by a spectrophotometrical meter. At this time, the sealing member  76  and the rotating seal  72  at the rotor  10  side contact with each other, so that sealing is accomplished in order to suppress any leakage of the liquid. 
     As explained above, such a centrifuge is used for the purposes of virus purification to produce a vaccine and elimination of fever-inducing agents. Specific examples of the sample  184  are influenza viruses, Japanese B encephalitis viruses, whooping-cough viruses, AIDS viruses, and hepatitis viruses, and a staring ingredient thereof is a cell picked up form a culture fluid or an animal, or one suspended in a liquid like a biological fluid. 
     U.S. Pat. No. 4,011,972 discloses a continuous flow centrifugal separation rotor which performs centrifugal separation while allowing a sample to be continuously flowed into a rotor which is rotating at high speed. A rotor main body is arranged in a rotor rotation chamber, and a mechanical seal member is arranged outwardly of a door of a centrifuge. A journal bearing is provided around an outer circumference of a tube member extending upwardly from the rotor and having plural sample passageways. A space between the outer circumference of the tube and the bearing is lubricated by a lubricant. The lubricant functions to disconnect the interior of the rotor rotation chamber and the exterior thereof, and to maintain a vacuum environment in the rotor rotation chamber. One mechanical seal member has a sealing configuration that a rotating seal and a fixation seal always contact with each other. According to U.S. Pat. No. 4,011,972, a sample is continuously filled in at a predetermined flow rate and collected while the rotor is in a high-speed rotation condition, so that such a rotor is called a continuous flow rotor. An example of such a commercially available rotor is a P32CT-type continuous rotor made by Hitachi Koki Co., Ltd. 
     According to the zonal centrifuge, it requires an attachment/removal work of a cap and a seal member to a shaft which is rotating in conjunction with a rotor. Such a work to the rotating shaft cannot be carried out efficiently if an operator is not skilled well even if the rotor is rotated at a low rotation speed. 
     Moreover, according to the conventional centrifuge  51   a , when a density gradient liquid and an extrusion liquid are filled and when the sample  184  is filled or collected, the rotor rotation chamber  55  is kept in an atmospheric pressure (with the door  56   a  being opened). Accordingly, airs flow into the rotor rotation chamber  55 , so that the interior of the rotor rotation chamber  55  is subjected to dew condensation, or temperature control becomes imperfect. 
     Further, according to the continuous rotor disclosed in U.S. Pat. No. 4,011,972, since the seal member is always in a contact condition, the seal member is easily worn, and a lifetime thereof is short. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in view of the foregoing circumstances, and it is an object of the present invention to provide a zonal centrifuge having superior workability and functionality. 
     To accomplish the object of the present invention described above, a centrifuge according to a first aspect of the present invention comprises: 
     a rotor having a sample storage chamber for storing a sample; 
     a rotor rotation chamber in which the rotor is provided; 
     a driving unit rotating the rotor; 
     a first tube which has one end connected to the sample storage chamber, and has a first passageway and a second passageway, the first passageway being for filling a density gradient liquid and the sample in the sample storage chamber and collecting the sample in the sample storage chamber, and the second passageway being for filling a liquid pushing out the sample in the sample storage chamber to the first passageway; 
     a first seal member which is connected to another end of the first tube, and has a first opening and a second opening communicated with the first passageway and the second passageway, respectively; 
     a second seal member which is so arranged as to face the first seal member, and has a third opening and a fourth opening which face the first opening of the first seal member and the second opening thereof, respectively; 
     a second tube which has a third passageway having one end connected to the second seal member and communicated with the third opening, and a fourth passageway communicated with the fourth opening; and 
     a joining/separating member which joins and separates the first seal member and the second seal member. 
     As the first seal member and the second seal member are joined together by the joining/separating member, the first passageway and the first opening become communicated with the third opening and the third passageway, and the second passageway and the second opening become communicated with the fourth opening and the fourth passageway, so that the sample storage chamber of the rotor becomes accessible through the third passageway and the fourth passageway; and 
     as the first seal member and the second seal member are separated from each other by the joining/separating member, the first passageway and the first opening are separated from the third opening and the third passageway, and the second passageway and the second opening are separated from the fourth opening and the fourth passageway. 
     For example, the joining/separating member comprises: 
     a first supporting member arranged over the rotor, and rotatably supporting the first tube; and 
     a second supporting member which movably supports the second tube in a direction toward the first tube and in a direction apart from the first tube; and 
     an operation member, and wherein 
     the second seal member moves in accordance with a manipulation of the operation member, and abuts and slides the first seal member which is rotating along with rotation of the rotor. 
     The first supporting member may comprise: 
     a bearing which is arranged over the rotor, and rotatably supports the first tube; and 
     a bearing supporting member formed in a cylindrical shape, and having an internal face supporting the bearing, 
     the second supporting member may comprise: 
     a cylindrical sleeve which has one end connected to the bearing supporting member, and has another end provided with a threaded face; 
     a tube fixing member which is formed in a cylindrical shape, has an internal face fixing the second tube, has one end slidably fitted to an internal face of the sleeve, and has another end provided with a larger-diameter part; and 
     an elastic member arranged between the sleeve and the larger-diameter part of the tube fixing member, and urging the tube fixing member toward a direction apart from the first tube, and 
     the operation member is formed in a cylindrical shape, has one end provided with a threaded face corresponding to the threaded face of the sleeve, and has another end provided with an abutment part which abuts another end of the tube fixing member. 
     As the operation member is fastened to the sleeve, the joining/separating member causes the abutment part of the operation member to abut another end of the tube fixing member and to push the tube fixing member, causes the tube fixing member to move the second tube and the second seal member connected to the second tube in a direction toward the first tube, and causes the second seal member to abut and slide the first seal member which is rotating along with rotation of the rotor; and 
     as the operation member is loosened from the sleeve, the joining/separating member causes the tube fixing member to be urged in a direction opposite to an axis of the first tube, causes the tube fixing member, the second tube and the second seal member connected to the second tube to move in a direction apart from the first tube, and causes the second seal member to be apart from the first seal member which is rotating along with the rotation of the rotor. 
     A lubricant filled in a space between the first tube and the bearing may separate the rotor rotation chamber from atmosphere, thus a depressurized condition may be maintained when an interior of the rotor rotation chamber is depressurized. 
     The first seal member may be provided in a sealed space. 
     The sealed space may be formed by the first tube, the bearing, the bearing supporting member, and the second seal member. 
     It is desirable that two openings which are communicated with the sealed space should be formed in the bearing supporting member; 
     one opening should allow air passing through a filter to flow in; 
     another opening should suction the air; and 
     the air suctioned through another opening should be exhausted through another filter. 
     It is desirable that a member contacting the sealed space should be formed of a metal or a plastic which is a tolerant of heat at 121° C. 
     It is desirable that the bearing supporting member should have openings which reaches the bearing and from which a lubricant is supplied and/or collected. 
     Furthermore, it is desirable that the bearing supporting member should have an opening which reaches the bearing and from which a coolant is supplied. 
     A centrifuge according to a second aspect of the present invention comprises: 
     a rotor having a sample storage chamber for storing a sample; 
     a rotor rotation chamber in which the rotor is provided; 
     a driving unit rotating the rotor; 
     a first tube which has one end connected to the sample storage chamber, and has another end where a first seal member is provided; 
     a second tube so arranged as to face the first tube; 
     a second seal member arranged at one end of the second tube; and 
     a joining/separating member which joins and separates the first seal member and the second seal member with the rotor rotating chamber being in a depressurized condition. 
     A centrifuge according to a third aspect of the present invention comprises: 
     a rotor having a sample storage chamber for storing a sample; 
     a rotor rotation chamber in which the rotor is provided; 
     a driving unit rotating the rotor; 
     a depressurizing unit depressurizing the rotor rotation chamber; 
     a first seal member which has a opening for filling a density gradient liquid and the sample in the sample storage chamber and collecting the sample in the sample storage chamber; and 
     a second seal member which is so arranged as to face the first seal member, 
     wherein the first seal member joins and separates from the second seal member with the rotor rotating chamber being in a depressurized condition. 
     According to the present invention, it becomes possible to provide a centrifuge having superior workability and functionality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The object and other objects and advantages of the present invention will become more apparent upon reading of the following detailed description and the accompanying drawings in which: 
         FIG. 1  is a diagram showing a whole configuration of a centrifuge according to an embodiment of the present invention; 
         FIG. 2A  is an exemplary horizontal cross-sectional view showing an interior of a rotor when a density gradient liquid is filled; 
         FIG. 2B  is an exemplary vertical cross-sectional view showing the rotor when the density gradient liquid is filled and as viewed from a cross section of an arrow A-A in  FIG. 2A ; 
         FIG. 3  is a front vertical cross-sectional view enlargingly showing main parts of the centrifuge of the embodiment of the present invention when a sample is filled/collected; 
         FIG. 4  is a front vertical cross-sectional view enlargingly showing the main parts of the centrifuge of the embodiment of the present invention when centrifugal separation is carried out; 
         FIG. 5A  is a front vertical cross-sectional view showing a conventional centrifuge when a sample is filled/collected; 
         FIG. 5B  is a front vertical cross-sectional view showing the conventional centrifuge when centrifugal separation is carried out; 
         FIG. 6  is a front vertical cross-sectional view enlargingly showing main parts of the conventional centrifuge; and 
         FIG. 7  is a diagram showing procedures how to use the conventional centrifuge. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An explanation will be given of a centrifuge according to an embodiment of the present invention with reference to accompanying drawings. In order to clarify the explanation for the embodiment of the present invention, in a relationship between a tube and a rotor, a tube side is called an upward direction and a rotor side is called a downward direction in the embodiment. 
     As shown in  FIG. 1 , a centrifuge  51  comprises a casing  52  formed of sheet-metal parts, a driving unit  53 , a rotor  10 , and a rotor rotation chamber  55  all arranged in the casing  52 , a control panel  57  indicating an operating condition, and, an electrical control unit  60 , a vacuum evacuation device  62  and a rotor-chamber-interior cooling device  64  which are illustrated with a simplified contour respectively in the figure. 
     The rotor  10  stores a sample  184  subjected to separation and as shown in  FIGS. 2A ,  2 B. The rotor  10  is rotated and driven by the driving unit  53 , and separates the sample  184  in such a way that the sample  184  forms layers in the radial direction. As exemplary shown in  FIGS. 2A ,  2 B, the rotor  10  comprises a bowl-like rotor body  12 , tabular septa  16   b  which divides a sample storage chamber  18  storing the sample  184  in the rotor body  12  into four sectors as viewed from the above as shown in  FIG. 2A , and a cover  14 b which is located above the rotor body  12  and functions as a lid. Individual parts will be explained below in more detail. 
     The rotor body  12  has a male thread formed at an upper end portion of an outer circumference of the bowl-like contour, and has a rotation shaft opening  120  formed in a bottom face of the rotor body  12  and threaded with a rotation shaft  54 . 
     The septa  16   b  have a substantially cylindrical septa axis  160  and four plates  161  radially connected to the septa axis  160 , and are formed in an integral shape. The septa  16   b  are arranged in the rotor body  12 , and separates the sample storage chamber  18  into sector forms as viewed from above as shown in  FIG. 2A . The septa  16   b  have an opening which runs downwardly from the center of an upper face of the septa axis  160  and is bent in an L-shape to a side face of the septa axis  160 . This opening is a part of a sample passageway (first passageway)  300  to be discussed later for filling/collecting the sample  184  and a density gradient liquid to be discussed later. Moreover, an opening which runs downwardly from a part of the upper face of the septa axis  160  and is bent in an L-shape to a side face of the plate  161  facing the rotor body  12  is also formed. This opening is a part of an extrusion liquid passageway (second passageway)  320  for filling an extrusion liquid to be discussed later. 
     The cover  14   b  has a female thread fastened with the male thread of the rotor body  12 . As the cover  14   b  airtightly seals the opened portion of the bowl-like rotor body  12 , the sample  184  is stored. The sample storage chamber  18  is formed by the cover  14   b  and the rotor body  12 . Further, the cover  14   b  has an opening formed at the center thereof. A lower tube (first tube)  70   b  to be discussed later is attached in this opening. A lower end of the lower tube  70   b  is guided into the interior of the rotor  10  through this opening. 
     As shown in  FIG. 3 , the lower tube  70   b  has a dual-tube configuration comprised of a cylindrical inner tube  700  and a substantially cylindrical outer tube  701  having a larger-diameter part  702 . The larger-diameter part  702  of the outer tube  701  is so formed as to have a large diameter as it can be appropriately fitted into an oil bearing  80  to be discussed later. The lower tube  70   b  passes all the way through the opening formed at the center of the cover  14   b , and a lower end of the inner tube  700  is fitted into the opening formed in the upper face of the septa axis  160 . The lower tube  70   b  is fixed to the cover  14   b  by a tube fixing nut  78 . A rotating seal  72  (first seal member) which can be joined and separated from a fixing seal (second seal member)  25  provided at a seal member  21  (joining/separating member) to be discussed later is attached to an upper end of the lower tube  70   b . The rotating seal  72  is formed in a substantially cylindrical shape. The rotating seal  72  has an opening (first opening)  771  which is communicated with the interior of the inner tube  700  and an opening (second opening)  772  which is communicated with a space between the inner tube  700  and the outer tube  701 . 
     The rotating seal  72 , the lower tube  70   b  and the septa  16   b  having the foregoing configurations form the sample passageway  300  which runs from an upper face of the rotating seal  72  to the upper face center of the septa axis  160  via the inner tube  700 , runs downwardly from the upper face of the septa axis  160 , is communicated with the opening bent in an L-shape toward the side face of the septa axis  160 , and reaches the center of the sample storage chamber  18 . Furthermore, also formed is the extrusion liquid passageway  320  which runs from the upper face of the rotating seal  72 , passes through the space between an external face of the inner tube  700  and an internal face of the outer tube  701 , runs downwardly from a part of the upper face of the septa axis  160 , is communicated with the opening bent into an L-shape toward the side face of the plate  161  facing the rotor body  12 , and reaches the sample storage chamber  18  in the vicinity of an internal face of the rotor body  12 . 
     Next, an explanation will be given of the oil bearing  80  which separates the rotor rotation chamber in a vacuum condition from the atmosphere and a bearing housing (bearing supporting member)  82  which has a part for introducing a liquid cooling down a heat-generating part. Note that the oil bearing  80  and the bearing housing  82  configure a first supporting member. 
     A door  56   b  of the centrifuge  51   b  is attached with a bucket-like door adapter  560  which is a part where the bearing housing  82  is arranged. The door adapter  560  is attached in such a way that a protrusive portion thereof is fixed to the door  56   b  by a thread and the door adapter  560  protrudes downwardly of the door  56   b . The bearing housing  82  formed in a substantially cylindrical shape is attached to an internal bottom face of the door adapter  560 . The bearing housing  82  has a lower protrusive part  822  protruding outwardly at a bottom face thereof and has an upper protrusive part  824  protruding outwardly at an upper face. As a housing pushing plate  84  in abutment with an upper face of the lower protrusive part  822  is fastened to the internal bottom face of the adapter  560 , the bearing housing  82  is held by the housing pushing plate  84  in a sandwiched manner. The upper protrusive part  824  has a male thread formed at a side face thereof, and is fastened with a lower collar  23  of the mechanical seal member  21  to be discussed later. 
     The oil bearing  80  is fixed to an internal face of the bearing housing  82 . The larger-diameter part  702  of the outer tube  701  of the lower tube  70   b  is rotatably supported by the oil bearing  80  through a lubricant (lubricating agent) adhered to an internal face of the oil bearing  80 . Further, a coolant inlet connector  40 , a lubricant inlet connector  42 , a lubricant outlet connector  420 , an intake connector  44 , and an airflow inlet connector  440  are attached to an external face of the bearing housing  82 . Portions to which those connectors are attached are provided with openings  881 ,  882 ,  883 ,  884  and  885  which extend to an internal face of the bearing housing  82 , respectively. 
     First, an explanation will be given of the function of the oil bearing  80  and that of the lubricant inlet connector  42 . A space between the lower tube  70   b  and the oil bearing  80  is filled with a lubricant which is supplied from the lubricant inlet connector  42  and returns to the oil bearing  80  from the lubricant outlet connector  420 . Further, the lubricant not only functions as a lubricating agent, but also functions to separate the rotor rotation chamber  55  from the atmosphere. That is, the lubricant always seals the space between the oil bearing  80  and the lower tube  70   b . Accordingly, even if the rotor rotation chamber  55  is vacuumed when the rotor  10  is rotating at high speed, entering of an air from the upward of the rotor rotation chamber  55  is suppressed, and the vacuuming condition in the rotor rotation chamber  55  is maintained. A circumferential speed of the rotor  10  is about 20 m/s and is high if the maximum rotating speed of the rotor  10  is 35000 rpm, so that a temperature of the sliding part where the lower tube  70   b  and the oil bearing  80  are in contact with each other rises. An explanation will be given of the coolant inlet connector  40  which introduces a coolant that cools down the sliding part. 
     The coolant inlet connector  40  is attached to the external face of the bearing housing  82  as explained above. In the embodiment, the coolant inlet connector  40  is attached downwardly of the attached location of the lubricant inlet connector  42 . As explained above, the opening  881  extends from the coolant inlet connector  40  toward an internal face of the bearing housing  82 , and is communicated with the oil bearing  80 . The oil bearing  80  has a recess  800  which has a smaller outer diameter than other outer diameters and is placed in a portion contacting a coolant supplied from the coolant inlet connector  40 . The recess  800  increases a contacting area of the oil bearing  80  with the coolant, and is so formed that the coolant contacts a portion in the vicinity of the heat-generating sliding part between the oil bearing  80  and the lower tube  70   b , thereby efficiently cooling down the oil bearing  80 . Furthermore, the bearing housing  82  has a coolant opening  400  whose inlet is the coolant inlet connector  40  and whose outlet is a coolant outlet  401  to be discussed later opened in the mechanical seal member  21 . The coolant opening  400  extends in the radial direction of the bearing housing  82  from the recess  800  of the oil bearing  80 , is bent in an L-shape upwardly, and reaches the coolant outlet  401  formed in an upper face of the bearing housing  82 . 
     Next, an explanation will be given of the configuration of the intake connector  44  and that of the airflow inlet connector  440  which are used for detecting any leakage from an attachment/detachment part between the rotating seal  72  and the fixing seal  25  to be discussed later. The intake connector  44  is attached to the bearing housing  82 . The intake connector  44  is provided upwardly of the lubricant inlet connector  42 . The opening  884  communicating with the intake connector  44  is communicated with a housing space (sealed space)  820  which locates above the oil bearing  80  and is partitioned by the fixing seal  25  to be discussed later of the mechanical seal member  21  and the bearing housing  82 . The airflow inlet connector  440  is attached to a position which is symmetrical to the intake connector  44  relative to the tube  70   b . The opening communicating with the airflow inlet connector  440  is communicated with the housing space  820  like the opening communicating with the intake connector  44 . 
     Next, an explanation will be given of the mechanical seal member  21  of the embodiment. The mechanical seal member  21  has a function of joining and separating the fixing seal  25  to be discussed later and the rotating seal  72  from each other and of connecting/disconnecting the sample passageway  300  and a sample passageway (third passageway)  30  to be discussed later, and, the extrusion liquid passageway  320  and an extrusion liquid passageway (fourth passageway)  32 , between a state where the sample  184  mainly shown in  FIG. 3  is filled/collected and a state where centrifugal separation shown in  FIG. 4  is carried out. As shown in  FIGS. 3 and 4 , the mechanical seal member  21  mainly comprises a sleeve  22  to be discussed later, a lower collar  23  which fastens the sleeve  22  with the bearing housing  82 , a pressing member (tube fixing member)  29  which slides in the sleeve  22 , an upper collar (operating member)  24  which fastens the pressing member  29  with the sleeve  22 , an upper tube  90  (second tube) fitted to the center of the pressing member  29 , and a follower member  242  which followingly moves in accordance with movement of the pressing member  29 . Individual members will be explained in detail below. 
     The sleeve  22  is formed in a substantially cylindrical shape, has a larger-diameter part  220  formed at a lower end thereof, and has a male thread formed on an upper end face. The sleeve  22  slidably supports the pressing member  29  to be discussed later. 
     The lower collar  23  has a function of connecting the sleeve  22  and the bearing housing  82 . The lower collar  23  is formed in a substantially cylindrical shape having a through hole at the center. The lower collar  23  has an abutment part  230  protruding inwardly of the through hole at an upper part of the lower collar  23 , and has a female thread formed at an internal side face of a lower part. As the abutment part  230  abuts the upper protrusive part  824  of the bearing housing  82  and the female thread of the lower collar  23  is fastened with the male thread of the bearing housing  82 , the sleeve  22  is connected to the bearing housing  82  in a manner that the larger-diameter part  220  of the sleeve  22  is sandwiched. 
     The pressing member  29  is formed in a substantially cylindrical shape, has a through hole formed in the center thereof where the upper tube  90  to be discussed later is fitted in, and has a larger-diameter part  291  formed at a part of a side face. An upper spring (elastic member)  28  which is a coil spring is provided between the larger-diameter part  291  of the pressing member  29  and an upper face of the sleeve  22 . The upper spring  28  biases the pressing member  29  upwardly so that the pressing member  29  abuts the upper collar  24  to be discussed later. Selected for the upper spring  28  is one which has an appropriate size and elastic force so that a seal face of the rotating seal  72  and that of the fixing seal  25  contact with each other when the upper collar  24  is fastened and the seal face of the rotating seal  72  and that of the fixing seal  25  become apart from each other when the upper collar  24  is loosened. A coolant opening  402  which passes all the way through a part of the pressing member  29  from the downward direction to the upward direction is formed. The coolant opening  402  is provided in order to drainage the coolant which has cooled down the fixing seal  25  to be discussed later to the exterior. The coolant opening  402  is communicated with the coolant outlet connector  404  opened to the exterior of the centrifuge  51   b.    
     The upper collar  24  has a function of moving the pressing member  29  in the vertical direction. The upper collar  24  is formed in a substantially cylindrical shape having a through hole at the center thereof. The upper collar  24  has an abutment part  240  which abuts the larger-diameter part  291  of the pressing member  29  and formed at an upper part, and has a female thread corresponding to the male thread of the sleeve  22  and formed at an internal side face of a lower part. As the abutment part  240  abuts the larger-diameter part  291  of the pressing member  29  and the female thread of the upper collar  24  is fastened with the male thread of the sleeve  22 , the upper collar  24  biases a protrusive part of the pressing member  29  downwardly, and the pressing member  29  is moved downwardly against biasing of the upper spring  28 . In contrast, as the female thread of the upper collar  24  is screwed down from the male thread of the sleeve  22 , the upper spring  28  pushes the protrusive part of the pressing member  29  upwardly, so that the pressing member  29  is moved upwardly. 
     The upper tube  90  has a function of introducing a filled density gradient liquid, sample  184  and extrusion liquid into the lower tube  70   b  and a function of guiding the sample  184  to be collected from the lower tube  70   b . The upper tube  90  has a dual tube configuration comprised of a cylindrical inner tube  900  and a substantially cylindrical outer tube  901  partially having a larger-diameter part  902 . The larger-diameter part  902  of the outer tube  901  is formed to have a larger diameter so that it can be appropriately fitted into the foregoing pressing member  29 . The fixing seal  25 , which can be joining and separating from the rotating seal  72  provided at the upper end of the lower tube  70   b , is attached to a lower end of the upper tube  90 . The fixing seal  25  is formed in a substantially cylindrical shape, and has an opening (third opening)  773  communicating with the interior of the inner tube  900  and an opening (fourth opening)  774  communicating with a space between the inner tube  900  and the outer tube  901 . 
     A filling/collecting adapter  46  having a sample inlet/outlet connector  460  and an extrusion liquid inlet connector  461  is fitted to an upper end of the upper tube  90 . The sample inlet/outlet connector  460  has an opening communicating with the inner tube  900 . The extrusion liquid inlet connector  461  has an opening communicating with a space between the inner tube  900  and the outer tube  901 . The filling/collecting adapter  46 , the upper tube  90 , and the fixing seal  25  having the foregoing configurations form the sample passageway  30  which runs from the sample inlet/outlet connector  460  to the fixing seal  25  via the inner tube  900 . Moreover, the extrusion liquid passageway  32  which runs from the extrusion liquid inlet connector  461  to the fixing seal  25  through a space between an external face of the inner tube  900  and an internal face of the outer tube  901  is also formed. 
     The follower member  242  has a fixing seal body  26  which supports the fixing seal  25  at a central lower face. A lower coil spring  27  which is a coil spring is provided between the follower member  242  and the pressing member  29 . The follower member  242  is biased as the lower spring  27  expands or contracts in accordance with a position of the pressing member  29 , and slides over the internal face of the bearing housing  82 . Selected for the lower spring  27  is one which has an appropriate size and elastic force so that the seal face of the rotating seal  72  and that of the fixing seal  25  contact with each other when the upper collar  24  is fastened and the seal face of the rotating seal  72  and that of the fixing seal  25  are apart from each other when the upper collar  24  is loosened. Depending on a position of the follower member  242 , the fixing seal  25  becomes joined and separated from the rotating seal  72 . Further, regardless of the deformation amount, the lower spring  27  is set in such a way that the fixing seal  25  is pressed against the rotating seal  72  with almost constant pressing force. Accordingly, the fixing seal  25  is not pressed against the rotating seal  72  beyond necessity, and the contact pressure is maintained almost constant. Since the fixing seal  25  closely contacts the rotating seal  72  which is in rotation when the sample  184  is filled/collected, heat is generated at a sliding face between the rotating seal  72  and the fixing seal  25 . Accordingly, a seal cooling space  210  is provided for cooling down the fixing seal  25  by contacting a coolant to the fixing seal  35 . The seal cooling space  210  is segmented by the fixing seal body  26 , the bearing housing  82 , the sleeve  22 , and the pressing member  29 . Moreover, contact pressure of the fixing seal  25  and the rotating seal  72  can be given by an addition of the elastic force of the lower spring  27  and water pressure when water flows. 
     Next, an explanation will be given of an operation of the centrifuge of the embodiment. 
     First, a step of filling a sample will be explained. The control panel  57  is manipulated to vacuum (depressurize) the rotor rotation chamber  55 , and to cause the drive unit  53  shown in  FIG. 1  to rotate the rotor  10  at about 3000 rpm. Next, the upper collar  24  shown in  FIG. 3  is screwed in the sleeve  22  to move the pressing member  29  downwardly. The pressing member  29  moves downwardly, while at the same time, the upper tube  90  fitted to the pressing member  29  also moves downwardly. Then, the fixing seal  25  attached to the lower end of the upper tube  90  is joined with the rotating seal  72  attached to the upper end of the lower tube  70   b . In this fashion, the sample passageway  30  and the sample passageway  300  are connected together. Next, using a liquid-feeding pump (not shown), a density gradient liquid necessary for separating a sample and the sample  184  subject to separation are filled from the sample inlet/outlet connector  460 .  FIG. 2B  is a schematic view showing the interior of the rotor  10  when the density gradient liquid is filled. The figure shows a state where three steps of density gradient liquids ( 181 ,  182 , and  183  in the order of higher specific gravity) are filled. Thereafter, the sample  184  subject to separation is filled from the sample inlet/outlet connector  460  which is shown in  FIG. 3  and communicated with the center of the rotor  10  via the sample passageway  300 . Furthermore, a liquid  185  having a lighter specific gravity than that of the sample  184  is filled to perpendicularly raise the sample  184  subject to separation as shown in  FIG. 2B . A preparation for centrifugal separation is completed through the foregoing works. 
     Next, a step of performing centrifugal separation will be explained. As the upper collar  24  is rotated in a direction in which the fastening with the sleeve  22  is loosened following to the sample-filled state shown in  FIG. 3 , the upper collar  24  is moved upwardly. The pressing member  29  urged toward the upper collar  24  by the upper spring  28  also moves upwardly while abutting the upper collar  24 . Further, the upper tube  90  fitted to the pressing member  29  also moves upwardly, and the fixing seal  25  attached to the lower end of the upper tube  90  also moves upwardly. Accordingly, as shown in  FIG. 4 , the fixing seal  25  of the upper tube  90  becomes apart from the rotating seal  72  of the lower tube  70   b , thus suppressing generation of any large sliding friction originating from the joining of both seals when the rotor  10  is rotating at high speed. Next, the rotor rotation chamber  55  is vacuumed, the rotation speed of the rotor  10  is increased to a predetermined rotation speed, and centrifugal separation with a time appropriate for separating the sample  184  is then carried out. 
     Next, a step of collecting the sample  184  will be explained. The rotation speed of the rotor  10  is reduced to 3000 rpm again. Next, as the upper collar  24  is screwed in the sleeve  22 , the pressing member  29  is caused to move downwardly. The pressing member  29  moves downwardly, while at the same time, the upper tube  90  fitted to the pressing member  29  moves downwardly. This causes the fixing seal  25  attached to the lower end of the upper tube  90  to contact the rotating seal  72  attached to the upper end of the lower tube  70   b . In this fashion, the sample passageway  30  and the sample passageway  300 , and, the extrusion liquid passageway  32  and the extrusion liquid  320  are respectively connected together. Next, an extrusion liquid is filled from the extrusion liquid connector  461 . The filled extrusion liquid flows into the external side (internal side-face side of the rotor body  12 ) of the sample storage chamber  18  through the extrusion liquid passageway  32  and the extrusion liquid passageway  320 . The flowing extrusion liquid pushes the sample  184  from the external side of the sample storage chamber  18  to the internal side thereof. The pushed sample  184  is pushed out from the sample inlet/outlet connector  460  through the sample passageway  300  and the sample passageway  30 , and then collected. The density gradient liquid containing settling particles can be dividingly collected by a fraction collector while continuously measuring a light absorption degree through a spectrophotometric meter or the like. In the successive foregoing steps, the rotor rotation chamber  55  is airtightly sealed from the atmosphere by the lubricant filled in a space between the oil bearing  80  and the bearing housing  82 . 
     A step of monitoring any leakage of the sample  184  will be explained. An air filter (not shown) is connected in front of the airflow inlet connector  440  shown in  FIGS. 3 and 4  to make it possible to provide clean air from the airflow inlet connector  440 . Next, suctioning is carried out from the intake connector  44  through the housing space  82  using a suction pump, and the suctioned air is fed to an intake line. As the condition of the intake line is visually observed, any leakage caused by a contact failure of the rotating seal  72  and the fixing seal  25  can be monitored. Moreover, the air suctioned by the suction pump is cleanly exhausted through the air filter. Further, an inert gas (e.g., a nitrogen gas) may be supplied from the airflow inlet connector  440 . 
     A step of cooling down the oil bearing  80  and the fixing seal  25  both generating heats will be explained. A coolant supplied from the coolant inlet connector  40  cools down the external face of the oil bearing  80 , and then enters the seal cooling space  210  of the mechanical seal member  21  from the coolant outlet  401  provided at the upper end of the bearing housing  82  through the coolant opening  400  formed in the bearing housing  82 . The coolant entering the seal cooling space  210  cools down a side of the fixing seal  25  opposite to a side facing the rotating seal  72 , and is drained to the exterior of the centrifuge  51   b  through the coolant opening  402  formed in the pressing member  29  and the coolant outlet connector  404 . 
     The centrifuge  51   b  of the embodiment has the mechanical seal member  21  which causes the rotating seal  72  of the rotor  10  and the fixing seal  25  of the mechanical seal member  21  not to be in contact with each other when the rotor  10  shown in  FIGS. 1 and 4  is rotating at high speed (at the time of centrifugal separation). This extends the lifetime of the rotating seal  72  and that of the fixing seal  25  which are shortened by sliding friction. 
     Since the space between the oil bearing  80  and the bearing housing  82  is filled with the lubricant, the rotor rotation chamber  55  can be always decoupled from the atmosphere. This suppresses any inflow of air from the above of the oil bearing  80  even if the rotor rotation chamber  55  is vacuumed when the rotor  10  is rotating at high speed. Thus, the vacuuming condition of the rotor rotation chamber  55  can be maintained. 
     The joining and separation of the rotating seal  72  and the fixing seal  25  can be adjusted by the upper collar  24  which is present in the atmosphere without directly touching a space where the sample is present. As the bearing housing  82  and the mechanical seal member  21  are combined together, as shown in  FIG. 3 , the surroundings around the seal faces can be a sealed space. The adjustment of the joining and separation of the rotating seal  72  and the fixing seal  25  utilizes a screwing connection of the upper collar  24  and the sleeve  22  in the embodiment. However, other techniques can be used if such a purpose can be accomplished, and the same effect can be achieved in this case. For example, a sealed space may be formed around the upper collar  24 , and the position of the upper collar  24  may be adjusted by the pressure of air supplied to the sealed space. This enables remote setting of the air pressure and remote adjustment of the joining and separation. 
     The explanation has been given of the configuration that the fixing seal  25  becomes joined and separated from the rotating seal  72  in the embodiment, but the functional contribution can be freely changed if the fixing seal  25  and the rotating seal  72  can be joined and separated from each other, and a configuration that the rotating seal  72  becomes joined and separated from the fixing seal  25  may be employed. 
     There is no problem if the intake connector  44  and the airflow inlet connector  440  are not equipped. However, by providing such connectors, it becomes possible to monitor any leakage caused by a contact failure of the rotating seal  72  and the fixing seal  25 , so that the maintenance of the centrifuge  51   b  is facilitated. According to the embodiment, air passing through the air filter is caused to flow in from the airflow inlet connector  440 , and is exhausted from the intake connector  44  through the filter. Accordingly, even if the mechanical seal member  21  is falsely attached or seal-relating parts are worn or damaged, it is possible to suppress any inflow of contaminated substances in air into the sample passageway, thus suppressing any contamination of the sample  184 . 
     Furthermore, by equipping the coolant inlet connector  40 , the coolant openings  400 ,  401 , the coolant outlet  401 , and the coolant outlet connector  404 , a coolant can be guided to the oil bearing  80  and the fixing seal  25  to efficiently cool down those parts. 
     Note that members configuring the rotating seal  72 , the fixing seal  25  and the mechanisms thereof are formed of a metal or a plastic which can be tolerant of heat at least 121° C. Accordingly, even when the sample  184  leaks because of a failure of such a part and the surroundings of such a part are contaminated by the sample  184 , if vapor steam is introduced from the airflow inlet connector  440 , steam sterilization for 20 minutes can be carried out at 121° C. by controlling a temperature and pressure at the intake connector  44  side. This enables the user to easily sterilize the surroundings of the seal faces, so that the user can work efficiently when disassembling and cleaning the centrifuge  51   b.    
     As the fastening of the lower collar  23  and the bearing housing  82  is loosened and those parts are disassembled from each other, the mechanical seal member  21  can be removed from the bearing housing  82 , so that the centrifuge  51   b  of the embodiment has good maintenance property and accommodation property. 
     The centrifuge  51   b  of the embodiment has the space between the oil bearing  80  and the bearing housing  82  where the lubricant is filled, and the rotor rotation chamber  55  is separated from the housing space  820  by the lubricant. The fixing seal  25  and the rotating seal  72  can be joined and separated from each other within the housing space  820 , so that it is not necessary to open the rotor rotation chamber  55 . Accordingly, a pressure in the rotor rotation chamber  55  can be reduced right after the operation is started (a start switch of the control panel  57  is turned ON) without causing any dew condensation inside the rotor rotation chamber  55 , so that the operation time can be shortened (the pressure of the rotor rotation chamber  55  can be reduced while the rotor  10  is rotated at 3000 rpm and a density gradient liquid and the sample  184  are filled). Further, regardless of any effect of the atmosphere, the temperature of the interior of the rotor rotation chamber  55  can be controlled precisely. 
     Although the explanation has been given on a case in the embodiment where the centrifuge  51   b  of the embodiment has one sample passageway  300  and one extrusion liquid passageway  320  in the septa  16   b , a plurality of such passageways may be formed respectively. 
     Various embodiments and changes may be made thereunto without departing from the broad spirit and scope of the invention. The above-described embodiment is intended to illustrate the present invention, not to limit the scope of the present invention. The scope of the present invention is shown by the attached claims rather than the embodiment. Various modifications made within the meaning of an equivalent of the claims of the invention and within the claims are to be regarded to be in the scope of the present invention. 
     This application is based on Japanese Patent Application No. 2008-255740 filed on Sep. 30, 2008, and including specification, claims, drawings and summary. The disclosure of the above Japanese Patent Application is incorporated herein by reference in its entirety.