Patent Publication Number: US-9839729-B2

Title: Blood bag system and cassette

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 13/131,054 filed on May 25, 2011, which is a U.S. national stage application based on International Application No. PCT/JP2009/069894 having an international filing date of Nov. 18, 2009 and which claims priority to Japanese Application No. 2008-305211 filed on Nov. 28, 2008, the entire content of each of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a blood bag system and a cassette to be mounted in a centrifugation and separation apparatus or the like, for centrifuging whole blood or a blood component (buffy coat or the like) prepared from whole blood into a supernatant liquid and a sedimentary liquid and transferring the supernatant liquid. 
     BACKGROUND ART 
     Hitherto, whole blood transfusion in which all the components of blood obtained by blood donation are subjected to transfusion has been the mainstream of blood transfusion. Attendant on the recent progress of technologies, however, blood component transfusion has come to be conducted in which the obtained blood is divided into blood components, such as red blood cells, platelets and plasma, and only the blood component needed by a patient is subjected to transfusion. With blood component transfusion, it is possible to alleviate the burden on the patient&#39;s circulatory system and other side effects, and effective utilization of the donated blood is promised. 
     When subjected to centrifugation, the donated blood is divided into a light supernatant PRP fraction, a heavy sedimentary CRC fraction, and a buffy coat (BC) formed therebetween. The buffy coat contains white blood cells, platelets and red blood cells, and in particular, the platelets include young active platelets in high proportion. 
     On the other hand, the buffy coat contains white blood cells and therefore cannot be utilized as is. In view of this, it is a common practice to extract only the buffy coat from the centrifuged blood, to subject it again to centrifugation so as to separate the buffy coat into a supernatant liquid and a sedimentary liquid, and further to remove white blood cells from a supernatant liquid by a white blood cell removing filter (see, for example, Patent Document 1). 
     Patent Document 1 
     Japanese Laid-Open Patent Publication No. 07-507717 (PCT) (WO93/25295A1) 
     SUMMARY 
     In order to centrifuge a buffy coat into a supernatant liquid and a sedimentary liquid and to transfer the supernatant liquid as mentioned above, it is necessary to perform centrifugation in a former step and to separate (transfer) in a latter step. Accordingly, two special purpose apparatuses are needed therefor, with troublesome operations. 
     It is preferable that a centrifugation and separation apparatus, which is capable of simultaneously carrying out the two steps, is put to practical use. As such a centrifugation and separation apparatus, a centrifugation means and a separation means (transfer means) may be provided, so that a desired treatment will be carried out by use of a predetermined disposable blood bag system. As for such a blood bag system to be used in the centrifugation and separation apparatus, in general, the following configuration may be considered. The system includes a first bag in which the buffy coat is reserved and in which the buffy coat is centrifuged into a supernatant liquid and a sedimentary liquid, a filter for removing white blood cells from the supernatant liquid transferred by pressing the first bag by a predetermined pressing means, a second bag for reserving the supernatant liquid deprived of the white blood cells by the filter, a first tube for connecting the first bag and an inlet of the filter, a second tube for connecting the second bag and an outlet of the filter, and a first clamp and a second clamp for closing and opening the first tube and the second tube. 
     In order to mount such a blood bag system in a centrifugation and separation apparatus, however, the first bag, the second bag and the filter must be disposed in appropriate positions, and the first tube, the second tube, the first clamp and the second clamp must be disposed along appropriate paths. This leads to a complicated procedure as well as a fear of mismounting. 
     The present invention has been made in consideration of the above-mentioned problems. Accordingly, it is an object of the invention to provide a blood bag system and a cassette therefor to be mounted in a centrifugation and separation apparatus for centrifuging a buffy coat obtained from whole blood into a supernatant liquid and a sedimentary liquid and transferring the supernatant liquid, wherein the blood bag system and the cassette can be mounted in the centrifugation and separation apparatus readily and accurately. 
     According to the present invention, there is provided a blood bag system including a first bag for reserving whole blood or a blood component, a filter having a filter medium for removing predetermined cells from a blood component obtained by centrifugation of the liquid contained in the first bag, a second bag for reserving a blood component obtained upon removal of the predetermined cells by the filter, a first tube for connecting the first bag and an inlet of the filter, a second tube for connecting the second bag and an outlet of the filter, and a cassette for holding a part of the first tube and a part of the second tube, wherein the cassette has a first clamp section for closing and opening the first tube, and a second clamp section for closing and opening the second tube. 
     According to the present invention, there also is provided a cassette mounted to a multiple bag including a first bag for reserving whole blood or a blood component, a filter having a filter medium for removing predetermined cells from a blood component obtained by centrifugation of the liquid contained in the first bag, a second bag for reserving a blood component obtained upon removal of the predetermined cells by the filter, a first tube for connecting the first bag and an inlet of the filter, and a second tube for connecting the second bag and an outlet of the filter, wherein the cassette holds a part of the first tube and a part of the second tube, and includes a first clamp section for closing and opening the first tube, and a second clamp section for closing and opening the second tube. 
     Thus, the first tube and the second tube are preliminarily arranged properly in the cassette of the blood bag system, and it is sufficient simply to mount the cassette in a predetermined portion of the centrifugation and separation apparatus. Therefore, the need for intricate laying and arrangement of the first and second tubes, and the need for arranging the first and second clamps are eliminated, whereby mounting of the cassette can be carried out easily and assuredly. In addition, the cassette is equipped with the first clamp and the second clamp, and the clamps are arranged properly in relation to the clamp driving means within the centrifugation and separation apparatus. 
     The first clamp section and the second clamp section may be configured integrally with the cassette. This makes it possible to simply configure the first clamp section and the second clamp section, and to reduce the number of component parts through integral molding. Naturally, therefore, the operator does not need to mount the first clamp and the second clamp to the cassette, so that the cassette can be mounted easily, thereby reducing the possibility of mismounting. 
     A configuration may be adopted wherein the first clamp section and the second clamp section each includes a pressing section which can be elastically advanced and retracted, and which presses the first tube or the second tube from a lateral side thereof, an acute-angular engaged portion provided at a tip of the pressing section, a latch section which can be elastically tilted, and an engaging portion which is provided on the latch section and which engages with the engaged portion of the pressing section while in a state of pressing the first tube or the second tube. This enables the first clamp and the second clamp to be simple in configuration. 
     According to the present invention, there is further provided a blood bag system including a first bag for reserving whole blood or a blood component, a filter having a filter medium for removing predetermined cells from a blood component obtained by centrifugation of the liquid contained in the first bag, a second bag for reserving a blood component obtained upon removal of the predetermined cells by the filter, a first tube for connecting the first bag and an inlet of the filter, a second tube for connecting the second bag and an outlet of the filter, a first clamp for closing and opening the first tube, a second clamp for closing and opening the second tube, and a cassette for holding a part of the first tube, a part of the second tube, the first clamp and the second clamp, wherein the cassette has a first clamp operating section for operating the first clamp, and a second clamp operating section for operating the second clamp. 
     According to the present invention, there is also provided a cassette mounted to a multiple bag including a first bag for reserving whole blood or a blood component, a filter having a filter medium for removing predetermined cells from a blood component obtained by centrifugation of the liquid contained in the first bag, a second bag for reserving a blood component obtained upon removal of the predetermined cells by the filter, a first tube for connecting the first bag and an inlet of the filter, a second tube for connecting the second bag and an outlet of the filter, a first clamp for closing and opening the first tube, and a second clamp for closing and opening the second tube, wherein the cassette holds a part of the first tube and a part of the second tube, and includes a first clamp operating section for operating the first clamp, and a second clamp operating section for operating the second clamp. 
     Thus, the first tube and the second tube are preliminarily arranged properly within the cassette of the blood bag system, and it is sufficient for the cassette to be mounted in a predetermined portion of a centrifugation and separation apparatus. Therefore, the need for intricate laying and arrangement of the first and second tubes, and the need for arranging the first and second clamps are eliminated, whereby mounting of the cassette can be carried out easily and assuredly. In addition, the first clamp and the second clamp are held by the cassette, and therefore the clamps are properly arranged in relation to the clamp driving means within the centrifugation and separation apparatus. 
     In addition, general-purpose clamp or the like can be utilized as the first clamp and the second clamp. Since the first clamp and the second clamp are preliminarily held properly by the cassette, it is unnecessary for the operator to mount the first clamp and the second clamp onto the cassette. Therefore, the required procedure is easy to carry out, and moreover, there is no possibility of misarrangement. 
     The first clamp operating section and the second clamp operating section may be configured integrally with the cassette. 
     The first clamp operating section and the second clamp operating section may each includes a pressing section which can be elastically advanced and retracted, and which presses the first tube or the second tube from a lateral side thereof through the first clamp and the second clamp, an acute-angular engaged portion provided at a tip of the pressing section, a latch section which can be elastically tilted, and an engaging portion, which is provided on the latch section, and which engages with the engaged portion of the pressing section while in a state of pressing the first tube or the second tube through the first clamp and the second clamp. This enables the first clamp operating section and the second clamp operating section to be simple in configuration. 
     When the first clamp and the second clamp are arranged in parallel with each other within the cassette, a parallel arrangement surface can be utilized effectively, and good balance is secured. 
     It is preferable that whole blood or a blood component collected from a plurality of donors is reserved in the first bag, and the blood bag system is mounted in a centrifugation and separation apparatus for centrifuging the liquid contained in the first bag into a supernatant liquid and a sedimentary liquid, thereby removing a predetermined component from the supernatant liquid by the filter, and for transferring (separating) the supernatant liquid, deprived of the predetermined component, into the second bag. 
     A configuration may be adopted in which the centrifugation and separation apparatus includes a first sensor and a second sensor, each of which has a light emitting section and a light receiving section, and which detects the kind of liquid passing between the light emitting section and the light receiving section, the cassette has a sensor hole in which the first sensor and the second sensor are inserted, and the first tube is located so as to pass between the light emitting section and the light receiving section of the first sensor, whereas the second tube is located so as to pass between the light emitting section and the light receiving section of the second sensor. This makes it possible to assuredly detect the liquids present in the first tube and the second tube. 
     According to the blood bag system and the cassette pertaining to the present invention, the first tube and the second tube are preliminarily arranged properly within the cassette of the blood bag system, and it is sufficient for the cassette to be mounted in a predetermined portion of a predetermined centrifugation and separation apparatus or the like. Therefore, the need for intricate laying and arrangement of the first and second tubes, and the need for arranging the first and second clamps are eliminated, whereby the required mounting can be carried out easily and assuredly. In addition, the first clamp section and the second clamp section are provided in or the first clamp and the second clamp are held in the cassette, so that the clamp sections or clamps are properly arranged in relation to clamp driving means within the centrifugation and separation apparatus or the like. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a centrifugation and separation apparatus; 
         FIG. 2  is a partial enlarged perspective view of a centrifugal drum in the centrifugation and separation apparatus; 
         FIG. 3  is an exploded perspective view of an insert unit; 
         FIG. 4  is a plan view of a blood bag system according to a first embodiment of the present invention; 
         FIG. 5  is a plan view of a multiple bag system; 
         FIG. 6  is a partial enlarged plan view of the blood bag system according to the first embodiment; 
         FIG. 7  is a partial enlarged perspective view of the blood bag system according to the first embodiment, in a condition where a filter holder is expanded; 
         FIG. 8  is a partial enlarged perspective view of the blood bag system according to the first embodiment, in a condition where the filter holder is bent at 90°; 
         FIG. 9  is a perspective view of the vicinity of a sensor hole in a cassette; 
         FIG. 10A  is a plan view of a first clamp in an initial state,  FIG. 10B  is a plan view of the first clamp in a closed state, and  FIG. 10C  is a plan view of the first clamp during a returning motion thereof; 
         FIG. 11  is a perspective view of a hinge section and a tube engaging section of the cassette; 
         FIG. 12  is a partial enlarged side view of the blood bag system according to the first embodiment, in a condition where the filter holder is expanded; 
         FIG. 13  is an exploded perspective view of a filter and a holder body; 
         FIG. 14  is a schematic illustration of actions carried out in the centrifugation and separation apparatus; 
         FIG. 15  is a partial enlarged plan view of a blood bag system according to a second embodiment of the invention; 
         FIG. 16  is a partial enlarged perspective view of the blood bag system according to the second embodiment, in a condition where a filter holder is not bent; 
         FIG. 17  is a plan view of a first clamp operating section; 
         FIG. 18  is a partial enlarged plan view of a blood bag system according to a third embodiment of the invention; and 
         FIG. 19  is a partial enlarged plan view of a blood bag system according to a fourth embodiment of the invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A blood bag system and the cassette according to the present invention will be described below, in which embodiments thereof are shown and described with reference to the accompanying  FIGS. 1 to 19 . 
     Blood bag systems  10   a ,  10   b ,  10   c ,  10   d  and cassettes  50   a ,  50   b ,  50   c ,  50   d  according to first to fourth embodiments are respectively mounted in a centrifugation and separation apparatus  11  for centrifuging whole blood or a blood component (hereinafter, referred to as a buffy coat in the following embodiments) prepared from whole blood into a supernatant liquid and a sedimentary liquid, and for transferring the supernatant liquid. First, the centrifugation and separation apparatus  11  will be described. In the following description, the direction of arrow A in  FIG. 2  will be taken as a radial direction, and the direction of arrow B will be taken as a circumferential direction. Strictly speaking, the circumferential direction is the direction along the circular arc, as indicated by arrow B. For convenience of description, however, a direction orthogonal to the arrow A in the location being described will also be referred to as the circumferential direction. 
     As shown in  FIG. 1 , the centrifugation and separation apparatus  11  has a box-like shape, and includes a top cover  12  which can be opened and closed, a centrifugal drum (centrifugation means)  14  inside the apparatus, six unit insertion holes  16  arranged at regular angular intervals (60°) inside the centrifugal drum  14 , six insert units  18  inserted respectively in the unit insertion holes  16 , and six pressers (pressing means)  20  (see  FIG. 2 ), which are provided in a central area and which can be advanced and retracted in a rotational radial direction in relation to the insert units  18 . 
     The centrifugation and separation apparatus  11  is operated based on operations performed at a console section  22  provided at the front of the apparatus. Further, the centrifugation and separation apparatus  11  is controlled by a microcomputer (not shown) and can display predetermined information on a monitor  24 . 
     As shown in  FIG. 2 , a central body  14   a  of the central drum  14  has a holding lever  25 , which is urged by an elastic body and which holds an end portion of a cassette holder  38 , electrodes  27 , first rods  136  and second rods  138 , and a presser  20 . The first rods  136  and the second rods  138  are provided in two pairs, wherein among these rods, the rods on the first circumferential direction B 1  side constitute a first clamp driving means  17   a  for closing and opening a first clamp section  106  (see  FIG. 3 ), and the rods on the second circumferential direction B 2  side constitute a second clamp driving means  17   b  for closing and opening a second clamp section  108  (see  FIG. 3 ). The section shown in  FIG. 2  may be configured as a single unit, and six such units may be combined with each other along the circumferential direction. 
     As shown in  FIG. 3 , the insert unit  18  has a unit body  26 , a cover body  28 , and the blood bag system  10   a . The unit body  26  is a bottomed tube, which has a wide circular arc shape in top plan view and is open at the top, wherein a small chamber (first chamber)  30  on the inner diameter side and a large chamber (second chamber)  32  are partitioned from each other by an arcuate wall  34 . A buffy coat pooling bag (first bag)  54  to be described later is disposed within the small chamber  30 , while a platelet preserving bag (second bag)  58  and a sampling bag  76  are disposed within the large chamber  32 . The platelet preserving bag  58  has a surface area, which is enlarged for securing appropriate oxygen permeability for the platelets reserved therein, and which is set to be larger than the buffy coat pooling bag  54 . 
     The buffy coat pooling bag (BC pooling bag)  54 , the platelet reserving bag  58  and the sampling bag  76  are each formed, for example, by a method in which flexible sheet members made of a flexible resin such as polyvinyl chloride and polyolefin are laid on each other, and seal portions at the peripheral edges thereof are joined by fusing (heat fusing, high-frequency fusing) or adhesion in order to obtain a bag-formed body. 
     The small chamber  30  opens not only at the top but also on the inner diameter side. A filter pocket  36  for holding a filter  56  and an attachment  142 , which will be described later, are provided on the outer diameter side of the wall  34 . A plate-like cassette holder  38  that projects to the inner diameter side is provided at both end portions on the inner diameter side of the small chamber  30 . 
     The cassette holder  38  includes a first sensor  40  and a second sensor  42  for detecting the kinds of liquids that pass inside a first tube  60  and a second tube  62 , both to be described later, as well as detaching levers  44  and holder projections  45  provided on both ends in the circumferential direction. The first sensor  40  and the second sensor  42  include light emitting sections  40   a ,  42   a  (see  FIG. 9 ) and light receiving sections  40   b ,  42   b  (see  FIG. 9 ), wherein the kind of liquid passing between these sections can be determined based on the degree of transmission of light through the liquid. The light emitting sections  40   a ,  42   a  and the light receiving sections  40   b ,  42   b  are arranged in parallel with each other, and project slightly upwards at the top surface of the cassette holder  38 . A plurality of contacts (not shown) for connection to the first sensor  40  and the second sensor  42 , or to interface circuits thereof, are provided at a lower surface of the cassette holder  38 . When the contacts are placed in contact with the reception-side electrodes  27  (see  FIG. 2 ) provided on the central body  14   a  of the centrifugal drum  14 , signals from the first sensor  40  and the second sensor  42  can be supplied to the microcomputer. 
     The cover body  28  includes a cover, which is mounted to the unit body  26  from an outer lateral side thereof. The cover body  28  is capable of covering an outer lateral surface, an upper surface and a lower surface of the unit body  26 , and can securely hold the blood bag system  10   a  mounted on the unit body  26 . 
     Next, the blood bag system  10   a  and the cassette  50   a  according to the first embodiment will be described below. As shown in  FIG. 4 , the blood bag system  10   a  comprises a multiple bag  52  and a cassette  50   a.    
     As shown in  FIG. 5 , the multiple bag  52  includes the BC pooling bag  54  in which a buffy coat (blood component) is reserved and in which the buffy coat is centrifuged into a supernatant liquid (blood component) and a sedimentary liquid by the centrifugal drum  14 , a filter  56  for removing white blood cells (predetermined cells) from the supernatant liquid transferred by pressing the BC pooling bag  54  by the presser  20 , the platelet reserving bag  58  for reserving the supernatant liquid obtained upon removal of white blood cells by the filter  56 , a first tube  60  for connecting the BC pooling bag  54  and an inlet  56   a  of the filter  56 , and a second tube  62  for connecting the platelet reserving bag  58  and an outlet  56   b  of the filter  56 . The filter  56  preferably is provided with a mark thereon, which is indicative of the blood flow direction. 
     The filter  56  (see  FIG. 13 ) has a roughly elliptical thin plate-like shape, with the inlet  56   a  provided on a first surface side at one end thereof, and the outlet  56   b  provided on a second surface side at the other end thereof. Each of the inlet  56   a  and the outlet  56   b  comprises a tubular body, which is elongated in the same direction as the longitudinal direction of the filter  56 . Inside the filter  56 , a planar filter medium  57  (see  FIG. 14 ) is provided, for partitioning the inside into a first surface side and a second surface side, respectively. 
     The multiple bag  52  further includes a third tube  70  having an end portion to which a container  68  for a platelet preserving liquid can be connected, and having the other end thereof connected to the BC pooling bag  54 , a branched tube  74  which is branched (into six branches, for example, formed through bifurcation and trifurcation) from the third tube  70  and to which a plurality of BC bags  72  can be connected, the sampling bag  76  for sampling the liquid contained in the platelet preserving bag  58 , a fourth tube  78  for interconnecting the platelet preserving bag  58  and the sampling bag  76 , and a sampling tube  80  that branches from the fourth tube  78 . When the blood bag system  10   a  is mounted in the centrifugation and separation apparatus  11 , the third tube  70  is cut after fusing thereof to prevent leakage at a location near the BC pooling bag  54 . The portion left upon cutting forms a third tube  70   a  (see  FIG. 7 ). 
     The multiple bag  52  includes a clamp  82  provided in the vicinity of an end portion of the third tube  70 , a clamp  84  provided on the tip side relative to the branching portion of the third tube  70 , a clamp  86  provided in the vicinity of an end portion of the fourth tube  78 , and a clamp  88  provided for the sampling tube  80 . Each of the tubes in the blood bag system  10   a  is a transparent flexible resin tube. 
     The clamp  82 ,  84 ,  86 ,  88  are standard products, which have hitherto been used, and the tubes onto which they are mounted can be closed and opened by operating the clamp  82 ,  84 ,  86 ,  88  with one&#39;s fingers. It is recommendable to provide the clamp  82 ,  84 ,  86 ,  88  with different colors according to the position and/or the purpose of use thereof. At times of sterilization and storage of the blood bag system  10   a , each of the clamp  82 ,  84 ,  86 ,  88  is in an opened state, so that the inside of the multiple bag  52  is in a mutually connected and uniformly sterilized state. 
     Each of end portions of the third tube  70 , the branched tube  74 , and the sampling tube  80  is closed by a predetermined means, and is placed in a sterilized state obtained by being subjected to a predetermined sterilizing treatment (for example, irradiation with γ-rays) together with the cassette  50   a.    
     Incidentally, although for convenience of illustration it is shown in  FIG. 5  that the BC bag  72  and the container  68  can be connected to the multiple bag  52  lacking the cassette  50   a , in practice the BC bag  72  and the container  68  are connected in a condition where the cassette  50   a  is provided as the blood bag system  10   a  (see  FIG. 4 ), as will be described later. 
     Returning to  FIG. 4 , the blood bag system  10   a  includes the multiple bag  52  and the cassette  50   a . The cassette  50   a  is fitted with the first tube  60  and the second tube  62 . 
     As shown in  FIGS. 6, 7 and 8 , the cassette  50   a  includes a plate section  100  to be mounted to the cassette holder  38 , an arch section  102  for interconnecting both end portions on the outer side of the plate section  100 , and a filter holder  104  connected to a central portion on the outermost diameter side of the arch section  102 . The material of the cassette  50   a , for example, is PP (polypropylene), POM (polyoxymethylene), or the like. 
     The arch section  102  is shaped along the top end of the wall  34 , and the space surrounded by the outer end surface of the plate section  100  and the arch section  102  has the same shape as the upper surface portion of the small chamber  30 , thereby forming a bag hole  105  in which to insert the BC pooling bag  54 . A portion of the whole length part of the arch section  102  may be provided with an angled structure so as to enhance strength. 
     The plate section  100  includes the first clamp section  106  and the second clamp section  108  provided on the inner diameter side by integral molding, a sensor hole  110  which is provided at a roughly central portion and in which the first sensor  40  and the second sensor  42  are inserted, a first guide passage  112  for guiding the first tube  60 , a second guide passage  114  for guiding the second tube  62 , an auxiliary fixing section  116  for fixing the short third tube  70   a , and two pins (holding sections)  118  provided at an outer end portion. 
     The two pins  118  have an appropriate enlarged-tip shape, and are inserted in end holes of the BC pooling bag  54 , thereby fixing the end portions of the BC pooling bag  54 . The BC pooling bag  54  has an end portion fixed by the pins  118 , and a body portion inserted into the bag hole  105 . Each of the pins  118  may have a tip portion split in two, so as to form a narrow slit. Therefore, at the time of fixing the BC pooling bag  54 , the pins  118  can be inserted in the end holes by reducing the diameter thereof in a manner of narrowing the slit and, after insertion, the pins  118  can be returned to their initial state, so as to produce a slip-off preventive effect. 
     The auxiliary fixing section  116  is formed by walls making light contact with both side surfaces of the third tube  70   a , and is shaped so as to bend in the direction of an outer diameter thereof, after guiding the third tube  70   a  in an appropriate amount in the first circumferential direction B 1 , from an inner diameter side end portion of the BC pooling bag  54 . This ensures that, on the third tube  70   a , only a sufficiently short tip portion protrudes from the plate section  100  (see  FIGS. 7 and 8 ), and the direction of protrusion is outwards (namely, in the centrifugal direction A 1 ), so that the third tube  70   a  is not vibrated or moved during centrifugation. 
     The first guide passage  112  and the second guide passage  114  each has a groove shape, which is formed by walls provided on both sides substantially over the whole length thereof, and which is open on the upper side. The first guide passage  112  and the second guide passage  114  are provided with small slip-off preventive projections  117  at the open upper end portions thereof. 
     The first guide passage  112  extends in the direction of the inner diameter from an end portion of the BC pooling bag  54 , passes through the sensor hole  110 , is bent in the first circumferential direction B 1  in the vicinity of an inner diameter side end surface, immediately thereafter passes through the first clamp section  106 , is bent in the direction of the outer diameter in the vicinity of an end portion in the first circumferential direction B 1 , and reaches an outer diameter end of the plate section  100 , where the first guide passage  112  bends inwards so as to point toward the filter holder  104 . 
     The second guide passage  114  extends in the direction of the inner diameter from the sensor hole  110 , is bent in the second circumferential direction B 2  in the vicinity of an inner diameter side end surface, immediately thereafter passes through the second clamp section  108 , is bent in the direction of the outer diameter in the vicinity of an end portion in the second circumferential direction B 2 , and thereafter is bent toward a skew lateral side. 
     As shown in  FIG. 9 , in the sensor hole  110 , the first tube  60  and the second tube  62  each have upper surfaces thereof fixed stably by two arms  120  having tips bent slightly downwards, and extend respectively in the radial direction. The first tube  60  and the second tube  62  are arranged in parallel in the circumferential direction, in such a manner that gaps are secured at both side surfaces in the circumferential direction of the sensor hole  110 , and another gap is secured between the first tube  60  and the second tube  62 . When the cassette  50   a  is mounted on the cassette holder  38 , the first sensor  40  and the second sensor  42  are inserted into the gaps in the sensor hole  110 , the first tube  60  is disposed between the light emitting section  40   a  and the light receiving section  40   b , and the second tube  62  is disposed between the light emitting section  42   a  and the light receiving section  42   b . The light receiving section  40   b  and the light receiving section  42   b  are formed integrally. The first tube  60  and the second tube  62  are held by the four arms  120 , so as to remain stable irrespective of the orientation of the cassette  50   a . The gap in the circumferential direction between the two arms  120 , which are opposed to each other in the circumferential direction, is formed narrowly to such an extent that the first tube  60  and the second tube  62  can pass through the gap in a pressed-down state. As is apparent from  FIGS. 7 and 9 , the first clamp section  106  and the second clamp section  108  are disposed in the vicinity of the sensor hole  110 , and are provided on the downstream side of the first sensor  40  and the second sensor  42 . 
     As shown in  FIGS. 10A to 10C , the first clamp section  106  has a closing section (pressing section)  122 , which is provided as part of the first guide passage  112  at a portion on the first circumferential direction B 1  side of an inner circumferential end of the plate section  100  and which closes the first tube  60 , a latch section  124  for holding the closing section  122  during closure thereof, and a triangular projection  126  provided on a surface on an opposite side from the closing section  122 . As illustrated in  FIGS. 10A-10C , the pressing section  122  is fixed in a cantilever manner to a portion of the cassette. 
     The closing section  122  has a bulge portion (pressing portion)  128  for pressing the first tube  60  from a lateral side thereof, and an acute-angular engaged portion  130  provided at the tip of the bulge portion  128 . A base portion of the closing section  122  is formed sufficiently small in diameter, so that the bulge portion  128  can be elastically advanced and retracted substantially in the radial direction. The latch section  124  has an engaging portion  132  for engagement with the engaged portion  130  of the bulge section  128  in a state of pressing the first tube  60 , and an inclined surface  134  formed at the tip thereof. A direction perpendicular to the inclined surface  134  is oriented toward a skew inner side. Due to the presence of the inclined surface  134 , the latch section  124  has a tapered shape when viewed in plan. The latch section  124  is formed with a sufficiently small diameter at the base portion thereof, and can be elastically tilted. 
     The first clamp section  106  is thus configured simply. In addition, the first clamp section  106  is formed by integral molding with the cassette  50   a , so that it is unnecessary to provide the clamp as an independent component part, and a reduction in the number of component parts can be achieved. 
     As shown in  FIG. 10A , in the initial condition of the first clamp section  106 , the bulge portion  128  of the closing section  122  is separated from the first tube  60 , whereby the first tube  60  is placed in a conducting state. 
     As shown in  FIG. 10B , when the first rod  136  of the central body  14   a  is extended to press the closing section  122  from a lateral side and to displace the closing section  122 , the bulge portion  128  presses down the first tube  60  in cooperation with the projection  126 , so as to close the first tube  60 . In this instance, the engaged portion  130  engages with the engaging portion  132  by slightly tilting the latch section  124 . Thereafter, the closed state of the first tube  60  by the bulge portion  128  is maintained, even after the first rod  136  returns to its original position. 
     As shown in  FIG. 10C , when the second rod  138  is extended, the tip surface thereof slides on the inclined surface  134  and pushes outwardly toward a lateral side, and the latch section  124  is tilted, whereby the engaging portion  132  becomes disengaged from the engaged portion  130 , and the engaged state is released. Therefore, when the second rod  138  contracts to its original position, the first clamp section  106  is returned to the initial state shown in  FIG. 10A , and the first tube  60  is again placed in a conducting state. 
     Since the second clamp section  108  is symmetrical with the first clamp section  106 , detailed description thereof is omitted. By means of the second clamp section  108 , the second tube  62  can be closed and opened. When the blood bag system  10   a  is mounted on the centrifugation and separation apparatus  11 , the first clamp section  106  and the second clamp section  108  are operated by the first clamp driving means  17   a  and the second clamp driving means  17   b  of the central body  14   a  (see  FIG. 2 ). When the blood bag system  10   a  is not mounted, the first clamp section  106  and the second clamp section  108  can be operated manually. 
     As shown in  FIGS. 7 and 8 , the filter holder  104  has a hinge section  140 , an attachment  142 , and a tube engaging section  144 . 
     As shown in  FIG. 11 , the hinge section  140  is basically composed of a pair of ear pieces  146  opposed to each other in the circumferential direction, and a vertical wall (stopper)  148  provided on the base end side. A thin projection  150  projects in the direction of the outer diameter from the lower end of the vertical wall  148 . The vertical wall  148  enables the filter  56  to be set at a more accurate angle. 
     The pair of ear pieces  146  are provided on inner sides thereof with a pair of round shafts  152  that face toward each other above the projection  150 , a pair of small upper stoppers  154  provided at upper end portions on the outer diameter side, and a pair of small ride-over projections  156  provided at lower portions. As is apparent from  FIG. 11 , the round shafts  152  are constituted by shafts that extend in the circumferential direction, whereby the filter  56  can be tilted with reference to the round shafts  152 . 
     As shown in  FIG. 12 , since the round shafts  152  are provided at upper portions of the ear pieces  146 , it is possible to move the filter  56 , the outlet  56   b  and the attachment  142  to appropriately high positions in their expanded state. Further, when the assembly is placed on a table surface, such members exert only their own weights on the BC pooling bag  54 , and an excessive pressure is not exerted on the BC pooling bag  54 . 
     As shown in  FIG. 13 , the attachment  142  has a support plate  158 , which makes contact with and thereby supports one side surface in the longitudinal direction as well as the half upper portion and the half lower portion of the filter holder  104 , a hinge turning section  160  having a semicircular arc-like sectional shape that engages with the round shafts  152 , and an arm  162  connecting an end portion of the support plate  158  and the hinge turning section  160 . The arm  162  includes a quadrilateral hole  164 , in which the projection  150  is snugly inserted, and left and right reinforcement plates  166 . 
     The support plate  158  includes a pair of filter holding projections  168  provided on the inside surface so as to hold both surfaces of the filter  56 , tube holding projections  170  provided on the outside surface so as to hold the first tube  60  at three positions, a first semicircular notch portion (first fitting portion)  172  provided at an upper tip portion for fitting of the inlet  56   a  therein, and a second semicircular notch portion (second fitting portion)  174  provided at a lower base end portion for fitting of the outlet  56   b  therein. In a bent condition, the first semicircular notch portion  172  is disposed on the outer diameter side relative to the second semicircular notch portion  174 . 
     When the attachment  142  is fitted to the hinge section  140 , the hinge turning section  160  with the arm  162  directed downward is fitted over the round shafts  152  from a lateral side, and thereafter, the attachment  142  is pushed down by exerting some force thereon, while permitting the arm  162  to ride over the upper stoppers  154 . Thus, the attachment  142  is easily mounted in position. 
     Incidentally, the hinge section  140  is not limited to a shaft-like configuration based on the round shafts  152 . For example, a configuration may also be adopted in which a thin section or an elastic section is bent. 
     A tube engaging section  144  is provided at a portion adjacent to the hinge section  140  of the arch section  102 , for thereby holding the second tube  62  in an appropriate orientation. 
     According to the filter holder  104 , the filter  56  can be stably held by the attachment  142 , and the first tube  60  and the second tube  62  can be appropriately held by the tube holding projections  170  and the tube engaging section  144 . 
     In addition, when the hinge turning section  160  is turnably supported on the round shafts  152 , the attachment  142  and the filter  56  can be tilted into various states, inclusive of an expanded state (see  FIG. 7 ) in which the attachment  142  and the filter  56  are parallel to and substantially in the same plane as the cassette  50   a , and a bent state (see  FIG. 8 ) in which the attachment  142  and the filter  56  are bent at an angle of 90° relative to the cassette  50   a.    
     In the expanded (spread) state in which the attachment  142  and the filter  56  are substantially in the same plane as the cassette  50   a , further turning thereof is prevented by the upper stoppers  154 . Since the upper stoppers  154  are sufficiently small, however, the attachment  142  and the filter  56  may be turned beyond the upper stoppers  154 , if necessary, by exerting an appropriate force thereon. 
     In the condition where the attachment  142  and the filter  56  are bent at 90° relative to the cassette  50   a , a side surface of the arm  162  makes surface contact with the vertical wall  148 , whereby assured angular positioning is achieved. In this instance, the projection  150  is inserted into the quadrilateral hole  164 , whereby stability of the attachment  142  is enhanced. In addition, when an operation is performed to bend the attachment  142 , both side portions of the attachment  142  ride over the ride-over projections  156 , and an appropriate click feeling is obtained. Therefore, the operator can recognize that the attachment  142  has been set at an appropriate angle. 
     The tip of the projection  150  may be enlarged in diametral size, so that a more assured click feeling is produced when the projection  150  is inserted into the quadrilateral hole  164 , and so that the projection  150  is prevented from slipping off. 
     According to the aforementioned filter holder  104 , at times of storage and transportation of the blood bag system  10   a  and the like, by placing the attachment  142  and the filter  56  in an expanded state substantially in the same plane as the cassette  50   a , the assembly is made sufficiently thin. Accordingly, the assembly can be placed in a vinyl resin bag or the like, together with (for example, in a state of being stacked with) the BC pooling bag  54  and the platelet preserving bag  58 . Although such a packed-in-bag state is not shown in the drawings, it is apparent from  FIG. 4  that the blood bag system  10   a  can be contained in a folded state within a vinyl resin bag, which is slightly larger than the platelet preserving bag  58  that makes up the largest of the component parts in area. 
     Further, when buffy coats are introduced into the BC pooling bag  54  from a required number of BC bags  72 , by placing the attachment  142  and the filter  56  in an expanded state substantially in the same plane as the cassette  50   a , it is ensured that the system does not expand uselessly, and the system can be easily hung from a girdle stand. 
     On the other hand, it is preferable for the filter  56  to be preliminarily regulated in orientation when placed in use. Specifically, in order for white blood cells to be removed by the filter  56 , the flow direction is set such that the blood component is supplied through the inlet  56   a  and is guided out through the outlet  56   b.    
     According to the filter holder  104 , when the blood bag system  10   a  is mounted in the centrifugation and separation apparatus  11 , the system is used in a condition where the attachment  142  and the filter  56  are bent at 90° relative to the cassette  50   a . In addition, as shown in  FIG. 8 , the filter  56  is held such that the outlet  56   b  is on a proximal side relative to the hinge section  140 , whereas the inlet  56   a  is on a distal side relative to the hinge section  140 . Thus, the filter  56  is used in a condition where the flow direction is oriented against the centrifugal force. As a result, the supernatant liquid  176  flows against the centrifugal force into the filter  56 , whereby the flow velocity is suppressed appropriately, and white blood cells can be removed assuredly. 
     In addition, since the inlet  56   a  is located below and on the outer diameter side in relation to the outlet  56   b , the supernatant liquid  176  having flowed in through the inlet  56   a  initially collects in a lower portion of the interior of the filter  56 , on the outer side of a filter medium  57  (see  FIG. 14 ) disposed in the filter  56 , and spreads in the lumen of the filter  56  along an outer diameter side surface while the centrifugal force acts thereon. After the space on the outer side of the filter medium  57  is filled, the supernatant liquid  176  is filtered while passing through the filter medium  57  and is discharged through the outlet  56   b . Therefore, the supernatant liquid  176  is filtered while effectively utilizing the entire surface of the filter medium  57  inside the filter  56 . Accordingly, white blood cells can be removed more assuredly. 
     Furthermore, at the time of assembling the filter holder  104 , the orientation of the filter  56  is determined by the first semicircular notch portion  172 , in which the inlet  56   a  is fitted, and the second semicircular notch portion  174 , in which the outlet  56   b  is fitted, whereby misassembly can be prevented from occurring. 
     Next, a method of using the blood bag system  10   a  and the cassette  50   a  according to the first embodiment configured in the foregoing manner will be described below. 
     First, as shown in  FIG. 5 , the clamp  84  on the third tube  70 , the first clamp section  106  and the second clamp section  108  are closed. A required number of BC bags  72  are connected to the branched tube  74 , and the container  68  for the platelet preserving liquid is connected to the third tube  70 . Buffy coats (or whole blood) collected from different donors are reserved in the BC bags  72 , respectively. Then, the buffy coats are collected from the BC bags  72  into the BC pooling bag  54 . 
     Next, on the third tube  70 , the clamp  82  is closed whereas the clamp  84  is opened, whereby the platelet preserving liquid is transferred into the BC bags  72 , and the platelet preserving liquid is mixed into the buffy coats remaining in the BC bags  72 . 
     Further, the clamp  84  is closed and the clamp  82  is opened, whereby the buffy coats mixed together with the platelet preserving liquid are transferred into the BC pooling bag  54 . 
     The BC pooling bag  54  is pressed by hand, whereby the air inside the BC pooling bag  54  is transferred into the BC bags  72 . 
     Then, the third tube  70  is cut, after being fused and sealed in an anti-leaking manner, at a position near the BC pooling bag  54 . The remaining portion forms a short third tube  70   a , as shown in  FIG. 7 , and the third tube  70   a  is fixed in the auxiliary fixing section  116  so that the tip thereof is oriented in the centrifugal direction. The third tube  70   a  may be cut shorter than that shown in  FIG. 7 . 
     Subsequently, as shown in  FIG. 8 , the attachment  142  and the filter  56  are bent at 90° relative to the cassette  50   a . The filter holder  104  acts to accurately and stably hold the attachment  142  and the filter  56  in a state of being bent at 90°. Since, as mentioned above, the inlet  56   a  is located below and on the outer diameter side in relation to the outlet  56   b  when the attachment  142  and the filter  56  are bent at 90° relative to the cassette  50   a , the flow velocity is suppressed and the entire surface of the filter medium  57  inside the filter  56  is effectively utilized. 
     Furthermore, as shown in  FIG. 3 , the blood bag system  10   a  is mounted in the insert unit  18 . Specifically, the cassette  50   a  is mounted in the cassette holder  38  and held by the holder projections  45 , the BC pooling bag  54  is inserted into the small chamber  30 , the filter  56  and the filter holder  104  are inserted into the filter pocket  36 , and the platelet preserving bag  58  and the sampling bag  76  are inserted into the large chamber  32 . Incidentally, since the filter  56  is maintained quite stably in a state of being bent at 90° by the filter holder  104 , a configuration in which the filter pocket  36  is omitted, and the filter  56  and the filter holder  104  are kept in the large chamber  32 , may also be adopted, depending on design conditions. 
     In this case, as shown in  FIG. 9 , the first tube  60  and the second tube  62  are properly arranged in the sensor hole  110 . Therefore, the first tube  60  is appropriately clamped between the light emitting section  40   a  and the light receiving section  40   b  of the first sensor  46 , whereas the second tube  62  is appropriately clamped between the light emitting section  42   a  and the light receiving section  42   b  of the second sensor  42 . Naturally, the first tube  60  is not arranged at a detection position of the second sensor  42 , and the second tube  62  is not arranged at a detection position of the first sensor  40 . 
     The arch section  102  is stabilized by abutment and mounting thereof on the upper end surface of the wall  34 , so that the attachment  142  and the filter  56  suspended from the arch section  102  also are made stable. 
     In addition, the BC pooling bag  54  is supported by the two pins  118 , whereas the first tube  60  connected to the BC pooling bag  54  is fixed along the first guide passage  112 . Therefore, the first tube  60  is arranged and oriented in the inner diameter direction A 2 , as viewed from the BC pooling bag  54 . 
     Next, as shown in  FIG. 1 , the insert unit  18 , with the blood bag system  10   a  inserted therein, is inserted into the unit insertion hole  16  of the centrifugation and separation apparatus  11 . As a result, an end portion of the cassette  50   a  is fixed by the holding lever  25  (see  FIG. 2 ). In addition, the contacts of the first sensor  40  and the second sensor  42 , or interface circuits thereof, are placed in contact with the electrodes  27  (see  FIG. 2 ). 
     While six insert units  18 , basically, are mounted in the centrifugation and separation apparatus  11 , the number of insert units  18  may be five or less, so long as the insert units  18  are in balance (preferably, three or two at regular angular intervals). 
     When the insert unit  18  is inserted into the unit insertion hole  16 , the first clamp section  106  and the second clamp section  108  are disposed properly at corresponding positions facing the first clamp driving means  17   a  and the second clamp driving means  17   b  (see  FIG. 2 ), respectively. Since the first tube  60  and the second tube  62  are preliminarily arranged properly by the first guide passage  112  and the second guide passage  114  in relation to the first clamp section  106  and the second clamp section  108 , the first clamp section  106  and the second clamp section  108  can be properly closed and opened through the first clamp section  106  and the second clamp section  108  under actions of the microcomputer. 
     Thus, in a series of operations by which the blood bag system  10   a  and the cassette  50   a  are mounted, each of the tubes in the blood bag system  10   a  is preliminarily connected properly. Specifically, by means of the first guide passage  112  and the second guide passage  114  in the cassette  50   a , the first tube  60  and the second tube  62  are disposed properly in relation to the sensor hole  110 , the first clamp section  106  and the second clamp section  108 . Therefore, the operator does not require special knowledge or understanding of operations and procedures for arranging the tubes, whereby the operator can easily and speedily carry out mounting of the blood bag system  10   a , without possibility of mismounting. The first tube  60  and the second tube  62  are preliminarily arranged properly within the cassette  50   a . In practice, therefore, the operator will be able to mount the blood bag system  10   a  in the centrifugation and separation apparatus without referring to any manuals or the like. 
     Next, the cover  12  of the centrifugation and separation apparatus  11  is closed, whereupon a centrifugation step and a separation step (a transfer step) are performed by operating the console section  22 . 
     During automatic operation of the centrifugation and separation apparatus  11 , first, the centrifugal drum  14  is rotated to perform the centrifugation step. In this case, the first clamp section  106  and the second clamp section  108  are preliminarily closed. For enhancing security of operation, however, as shown in  FIG. 10B , the first rod  136  is extended initially so that the first clamp section  106  is placed in a flat state by the closing section  122 . The second clamp section  108  also is placed in a closed state in the same manner. 
     As shown in  FIG. 14 , during the centrifugation step, a centrifugal force is imparted to the buffy coat reserved in the BC pooling bag  54  inside the small chamber  30 . As a result, the sedimentary liquid  178  containing heavy blood cell components and the like is moved in the direction of the outer diameter, whereas the supernatant liquid  176  containing light platelet components and the like is moved in the direction of the inner diameter, whereby the liquids become separated from each other. The supernatant liquid  176  contains white blood cells. The sedimentary liquid  178  is deep red in color and low in transparency, while the supernatant liquid  176  is constituted by a somewhat yellow-white transparent matter. 
     The centrifugation and separation apparatus  11  shifts from the centrifugation step to the separation step. During the separation step, while the centrifugal drum  14  continues to rotate, the second rod  138  is extended once as shown in  FIG. 10C  so as to tilt the latch section  124  and release the engaged state, thereby returning the centrifugation and separation apparatus  11  to the initial condition shown in  FIG. 10A  and placing the first tube  60  in an open state. The second tube  62  also placed in an open state in the same manner. 
     Next, as shown in  FIG. 14 , the presser  20  is displaced in the centrifugal direction A 1  so as to press the BC pooling bag  54 . The internal volume of the BC pooling bag  54  is reduced while being clamped between the presser  20  and the wall  34 , whereby the liquid contained therein is discharged through the first tube  60 . In this instance, in the interior of the BC pooling bag  54 , the sedimentary liquid  178  is collected in the direction of the outer diameter, while the supernatant liquid  176  is collected in the direction of the inner diameter. Meanwhile, the first tube  60  is oriented in the direction of the inner diameter, so that only the supernatant liquid  176  is ejected into the first tube  60 . 
     The supernatant liquid  176  that is ejected into the first tube  60  flows past the location of the first clamp section  106 , which is in an open state, whereupon white blood cells are removed therefrom by the filter  56 . In this instance, since the filter  56  is set so that the inlet  56   a  is located below and on the outer diameter side relative to the outlet  56   b , the supernatant liquid  176  flows in a direction resistant to gravity and centrifugal force. Therefore, the flow velocity of the supernatant liquid  176  is suppressed, and removal of white blood cells can be achieved assuredly through effective utilization of the entire surface of the filter medium  57 . The supernatant liquid  176  having passed through the filter  56  flows past the location of the second clamp section  108 , which is in an open state, and is supplied into and reserved within the platelet preserving bag  58 . 
     It is desirable that the supernatant liquid  176  in the BC pooling bag  54  be transferred into the platelet preserving bag  58  as completely as possible. However, it is undesirable for the sedimentary liquid  178  to be transferred into the platelet preserving bag  58 . In view of this, the liquids that pass through the first tube  60  and the second tube  62  are monitored by the first sensor  40  and the second sensor  42 , and a control is carried out in order to prevent the sedimentary liquid  178  from being transferred into the platelet preserving bag  58 . 
     Specifically, the microcomputer monitors signals supplied thereto from the first sensor  40  and the second sensor  42 , determines transparency values of the liquids that pass through the first tube  60  and the second tube  62  based on the magnitudes of the signals, and distinguishes the supernatant liquid  176  and the sedimentary liquid  178  from each other by their respective transparencies. 
     When the BC pooling bag  54  is pressed by the presser  20  during the separation step, the supernatant liquid  176  is guided out into the first tube  60  at a beginning period, so it can be confirmed by the first sensor  40  and the second sensor  42  that the supernatant liquid  176  is flowing therein due to the transparency of the liquid. 
     While pressing of the BC pooling bag  54  by the presser  20  is continued, the supernatant liquid  176  in the BC pooling bag  54  flows out completely, and thereafter, the sedimentary liquid  178  is guided out. As a result, at first, the first sensor  40  detects that the liquid flowing through the first tube  60  is changed into the sedimentary liquid  178 . At this point in time, the separation step may be considered finished. In order to collect the platelets into the platelet preserving bag  58  as much as possible, however, it is desirable that portions of the supernatant liquid  176 , which remain in the first tube  60  and the second tube  62 , also are fed out into the platelet preserving bag  58 . From this point of view, after the sedimentary liquid  178  has been detected by the first sensor  40 , pressing by the presser  20  may be further continued for a predetermined period of time. 
     Next, upon elapse of a predetermined time period, when it has been detected by the second sensor  42  that the liquid flowing through the second tube  62  has changed into the sedimentary liquid  178 , the first rods  136  are extended (see  FIG. 10B ) in order to close the first clamp section  106  and the second clamp section  108 , thereby placing the first tube  60  and the second tube  62  in a closed state. Further, the centrifugal drum  14  is stopped, whereupon the separation step is finished. 
     Upon elapse of a predetermined period of time from detection of the sedimentary liquid  178  by the first sensor  40 , the sedimentary liquid  178  reaches the filter  56 , and portions of the supernatant liquid  176  which remain in the first tube  60  and the second tube  62  are fed out into the platelet preserving bag  58  accordingly. Incidentally, before the predetermined time period has lapsed, basically, the sedimentary liquid  178  will not reach the position of the second sensor  42  (namely, the position of the sensor hole  110 ). In order to prevent the sedimentary liquid  178  from mixing into the platelet preserving bag  58 , however, monitoring thereof by the second sensor  42  is performed. 
     Immediately upon detection by the second sensor  42  of transfer of the sedimentary liquid  178  into the second tube  62 , the first clamp section  106  and the second clamp section  108  are simultaneously placed in a closed state, so as to prevent the sedimentary liquid  178  from flowing further downstream. There is a slight time lag until the first clamp section  106  and the second clamp section  108  become fully closed after detection of the sedimentary liquid  178  by the second sensor  42 . In the course of the second tube  62 , however, the second clamp section  108  is located on a downstream side relative to the position of the sensor hole  110 , where the second sensor  42  is provided. Therefore, the sedimentary liquid  178  does not flow to the downstream side of the second clamp section  108 . Even if the sedimentary liquid  178  flows past the position of the second clamp section  108 , the sedimentary liquid  178  will not reach the platelet preserving bag  58 , because a certain distance is provided between the position of the second clamp section  108  and the platelet preserving bag  58 . 
     When the separation step is finished, and the centrifugal drum  14  is stopped completely in this manner, the cover  12  is opened. The insert units  18  are taken out by operating the holding levers  25 , and the blood bag systems  10   a  are taken out by detaching the cover bodies  28 . In this case, the cassette  50   a  can easily be detached from the cassette holder  38  simply by operating the detaching levers  44  (see  FIG. 3 ). 
     Further, the first tube  60  in the blood bag system  10   a  is cut after being fused at a position near the BC pooling bag  54 , whereby the BC pooling bag  54  serves as a blood product containing blood cell components. On the other hand, when the second tube  62  is cut after being fused at a position near the platelet preserving bag  58 , the platelet preserving bag  58  serves as a blood product containing platelets. The blood product of the platelet preserving bag  58  permits a portion thereof to be transferred into the sampling bag  76 , and to be served to a predetermined test or the like. 
     According to the blood bag system  10   a  and the cassette  50   a  of the first embodiment, as mentioned above, the cassette  50   a  has the first tube  60  and the second tube  62  preliminarily arranged properly therein, so that it is sufficient simply to mount the cassette  50   a  into the central body  14   a  of the centrifugation and separation apparatus  11 . Therefore, the need for intricate laying and arrangement of the first tube  60  and the second tube  62 , as well as the need for arranging the first clamp section  106  and the second clamp section  108 , are eliminated, and mounting can be carried out easily and assuredly. In addition, the cassette  50   a  includes the first clamp section  106  and the second clamp section  108 , which are disposed properly in relation to the first clamp driving means  17   a  and the second clamp driving means  17   b  within the centrifugation and separation apparatus  11 . 
     In addition, since the first clamp section  106  and the second clamp section  108  are formed by integral molding with the cassette  50   a , the first clamp section  106  and the second clamp section  108  can be configured easily, and such integral molding enables a reduction in the number of component parts. Naturally, the operator does not need to mount the first clamp section  106  and the second clamp section  108  to the cassette  50   a , so that the required procedure is simple and there is no fear of misarrangement. 
     The cassette  50   a  is fixed to the centrifugation and separation apparatus  11  such that the first tube  60  and the second tube  62  are partially set horizontally and oriented in the radial direction, and so that the blood components inside the tubes flow in the direction of the inner diameter. In these parts, the blood components flow against centrifugal force, so that the flow velocities thereof can be prevented from increasing excessively. 
     Further, the first tube  60  and the second tube  62  cross the sensor hole  110  on the upper side and in a radial direction, while being located to enable detection thereof by the first sensor  40  and the second sensor  42 . Thus, the liquids inside the first tube  60  and the second tube  62  can be detected reliably. 
     The two pins  118 , which serve as a holding section for the cassette  50   a , hold an end portion where the first tube  60  of the first bag is provided. As a result, the first tube  60  is oriented in the direction of the inner diameter, and the supernatant liquid  176 , which is collected in the direction of the inner diameter by the centrifugation step, can be transferred from the first tube  60  during the separation step. 
     The cassettes  50   a  each have the first clamp section  106  and the second clamp section  108  arranged in parallel with each other in the circumferential direction, on a side pointing toward the center of rotation of the centrifugal drum  14  of the centrifugation and separation apparatus  11 , whereby the first clamp driving means  17   a  and the second clamp driving means  17   b  can be arranged in a concentrated manner within the central body  14   a  at the rotating section. In addition, with the first clamp section  106  and the second clamp section  108  arranged side by side in the circumferential direction, the surface on the rotational center side of the cassette  50   a  is utilized effectively, and good balance is secured. Further, with the first clamp section  106  and the second clamp section  108  arranged in parallel with each other in the circumferential direction, the cassette  50   a  forms a single layer in which overlapping of the first tube  60  with the second tube  62  does not occur at any location, and further, the cassette  50   a  has a simple structure such that arrangement of the first tube  60  and the second tube  62  during the manufacturing stage is easy to carry out. 
     Since the cassette  50   a  includes the attachment  142  by which the filter  56  is held so as to be changed in orientation, orientations of the filter  56  during storage and during use thereof can be changed appropriately. 
     The blood bag system  10   a  and the cassette  50   a  are inexpensive configurations, which are suitable for disposable use. 
     Assembly, packaging and a sterilizing treatment of the blood bag system  10   a  are performed under a predetermined quality control by the manufacturer. The blood bag system  10   a  is assembled by a predetermined automatic machine, or is assembled manually by use of predetermined assembly jigs. Further, tests are preliminarily conducted by predetermined automatic testers, whereby an assured arrangement can be achieved. 
     Next, a blood bag system  10   b  and a cassette  50   b  according to a second embodiment will be described below. Components of the blood bag system  10   b  (and each of  10   c  and  10   d ) and the cassette  50   b  (and each of  50   c  and  50   d ), which are the same as those of the above-described blood bag system  10   a  and cassette  50   a , are denoted by the same reference characters used above, and detailed descriptions of such features are omitted. 
     The blood bag system  10   b  includes the cassette  50   b  and a multiple bag  52 . The multiple bag  52  is basically the same as that used in the blood bag system  10   a , except that a first tube  60  and a second tube  62  are provided together with a first clamp  200  and a second clamp  202 . 
     As shown in  FIGS. 15 and 16 , in place of the above-described first clamp section  106  and second clamp section  108  (see  FIG. 4 ), the blood bag system  10   b  has the first clamp  200  and the second clamp  202 , as well as a first clamp operating section  204  and a second clamp operating section  206 , for operating and placing the first clamp  200  and the second clamp  202  in closed and open states. 
     The first clamp  200  and the second clamp  202  make up means for closing and opening intermediate portions of the first tube  60  and the second tube  62 , similar to the above-described first clamp section  106  and second clamp section  108 . 
     As shown in  FIG. 17 , the first clamp  200  is a resin body provided at one end thereof with a latch section  200   a , which is short and bent back in a J-shape, and provided at the other end thereof with a closing section (pressing section)  200   b , which is somewhat longer and bent back in a U-shape. The first clamp  200  further is provided at an inside surface thereof with a projection  200   c , and at both ends thereof with holes in which to insert the first tube  60 . The projection  200   c  is located at a position slightly deviated from the center, and has a hole  200   f  therein. In an initial state, the closing section  200   b  is opened to an appropriate degree. 
     The latch section  200   a , the closing section  200   b  and the projection  220   c  correspond respectively to the latch section  124 , the closing section  122  and the projection  126  described above (see  FIG. 10A ). More specifically, when the closing section  200   b  is pushed in toward the inner side, the first tube  60  can be closed by a bulge portion  200   d  on the inside of the closing section  200   b  and the projection  200   c , while the closing section  200   b  is held by the latch section  200   a.    
     When an inclined surface  200   e  at the tip of the latch section  200   a  is pushed toward a lateral side (or if the inclined surface  200   e  is pushed by a rod or the like from a lateral side) and the latch section  200   a  is thereby tilted toward the lateral side, the closing section  200   b  is released from an engaged state and returns to its original position, thereby opening the first tube  60 . 
     The second clamp  202  has the same structure as the first clamp  200 . As for the first clamp  200  and the second clamp  202 , the same structures as in the above-mentioned clamp  82 ,  84 ,  86 ,  88  can be used. 
     The first clamp operating section  204  in the cassette  50   b  includes a first pressing section  208  for pushing in the closing section  200   b  by operation of a first rod  136 , and a second pressing section  210  that slides on an inclined surface  200   e  by operation of a second rod  138 , so as to tilt the latch section  200   a  toward a lateral side. The first pressing section  208  and the second pressing section  210  are thinned in the vicinity of base end portions thereof so as to have elasticity, and the first pressing section  208  and the second pressing section  210  can be elastically displaced substantially in the radial direction under operations of the first rod  136  and the second rod  138 . End faces, on an inner diametrical side of the first pressing section  208  and the second pressing section  210 , are formed as outside flat surfaces  208   a  and  210   a  substantially along the circumferential direction, so that such end faces are stably pressed by the first rod  136  and the second rod  138 . 
     The first pressing section  208  is provided with an inside flat surface  208   b  substantially along the circumferential direction, so as to be capable of easily pressing an inner diameter side portion of a tip portion of the closing section  200   b . The second pressing section  210  is provided with an inclined surface  210   b , which is suitable for sliding along the inclined surface  200   e  of the latch section  200   a.    
     The first clamp operating section  204  is provided with a clamp space  212  in which the first clamp  200  is held, while leaving a small gap. The clamp space  212  is shaped such that the first clamp  200  cannot be mounted therein in an erroneously deviated position, or in a reverse orientation. Specifically, the clamp space  212  is provided with a projection (columnar section)  201  that is inserted into the hole  200   f , whereby positioning of the first clamp  200  is achieved. Since the projection  200   c  and the hole  200   f  are each located at a position slightly deviated from the center, there is no possibility of the first clamp  200  being mounted in a reverse orientation. Within the clamp space  212 , a gap is secured, which permits the latch section  200   a  to be tilted toward a lateral side. 
     The second clamp operating section  206  is symmetrical in shape with the first clamp operating section  204 . The first clamp operating section  204  and the second clamp operating section  206  can be operated respectively by the first clamp driving means  17   a  and the second clamp driving means  17   b  (see  FIG. 2 ), and can be operated manually when the blood bag system  10   b  is not mounted within the centrifugation and separation apparatus  11 . 
     A first guide passage  112  and a second guide passage  114  in the cassette  50   b  of the blood bag system  10   b  are shorter than those in the above-described blood bag system  10   a . The first guide passage  112  and the second guide passage  114  are formed so as to extend through upper portions of a sensor hole  110 , to thereby guide the first tube  60  in a first circumferential direction B 1 , and the second tube  62  in a second circumferential direction B 2 . 
     In the blood bag system  10   b  and the cassette  50   b  configured as described above, the first tube  60  and the second tube  62  are preliminarily arranged properly, similar to the above-described blood bag system  10   a  and cassette  50   a . Therefore, it is sufficient for the cassette  50   b  to be mounted within the central body  14   a  of the centrifugation and separation apparatus  11 , and the need for intricate laying and arrangement of the first tube  60  and the second tube  62  is eliminated, so that mounting thereof can be carried out easily and assuredly. In addition, the cassette  50   b  includes the first clamp  200 , the second clamp  202 , the first clamp operating section  204 , and the second clamp operating section  206 , with such components being arranged properly in relation to the first clamp driving means  17   a  and the second clamp driving means  17   b  (see  FIG. 2 ) of the centrifugation and separation apparatus  11 . 
     In the blood bag system  10   b  and the cassette  50   b , conventionally used general-purpose clamp can be applied to the first clamp  200  and the second clamp  202  arranged, so that the operator can easily comprehend the clamping means during manual operation thereof. Further, in the case where the multiple bag  52  must be detached from the cassette  50   b  for some reason, the first tube  60  and the second tube  62  can be kept closed by the first clamp  200  and the second clamp  202 . 
     As shown in  FIG. 18 , a blood bag system  10   c  and a cassette  50   c  according to a third embodiment have respective configurations, which are obtained by omitting the arch section  102  and the filter holder  104  from the above-described blood bag system  10   a  and cassette  50   a.    
     As shown in  FIG. 19 , a blood bag system  10   d  and a cassette  50   d  according to a fourth embodiment have respective configurations, which are obtained by omitting the arch section  102  and the filter holder  104  from the above-described blood bag system  10   b  and cassette  50   b.    
     Omission of the filter holder  104  permits the cassettes  50   c ,  50   d  to be simpler in configuration. In this case, the filter  56  can be maintained in a proper attitude by the filter pocket  36 . 
     The blood bag systems  10   c ,  10   d  and the cassettes  50   c ,  50   d  have the same operational effects as those of the above-described blood bag system  10   a  and cassette  50   a.    
     The blood bag systems  10   a  to  10   d  and the cassettes  50   a  to  50   d  are applicable not only to a centrifugation and separation apparatus  11 , but also to a blood component collection apparatus, a whole blood collection apparatus, an automatic blood separation apparatus, etc. The liquid reserved in the BC pooling bag  54  is not limited to a buffy coat, and depending on the use thereof, whole blood (contained liquid) may be reserved therein. 
     The blood bag system and the cassette according to the present invention are not limited to the above-described embodiments, and it is a matter of course that various configurations could be adopted without deviating from the essence and gist of the invention.