Method of separating liquid

Abstract: A liquid separator of the present invention comprises a first plate member (2), a second plate member (3) forming a receiving portion between it and the first plate member for receiving a flexible liquid container (8) including liquid separated into the upper liquid layer and the lower liquid layer, and pushing means (7) for pushing the second plate member toward the first plate member, said pushing means automatically pushing the second plate member with gradually decreasing pressure after starting the discharge of the upper liquid layer from the flexible liquid container. Therefore, the upper liquid layer can be discharged from the flexible liquid container without disturbing the boundary between the upper and lower liquid layers in the flexible liquid container. Thus, the upper liquid layer can automatically and efficiently be taken out from the flexible liquid container without mixing with the lower liquid layer and without any complicated and troublesome manipulation. If the discharge of the upper liquid layer is automatically stopped with a sensor detecting the boundary between the upper and lower liquid layers, it is possible to decrease errors of the sensor caused by the disturbance of the boundary.

Description: This invention relates to a method of separating upper and lower liquid layers from each other stored in a flexible container. More particularly, it relates to a method of separating various blood portions or components such as blood plasma, red cells, etc. from blood stored in a flexible container such as a blood bag or the like. In recent years, component transfusion in which only a blood component required by a patient is transfused to the patient has been employed instead of whole blood transfusion. On the other hand, blood plasma is collected for producing plasma preparations. A blood bag system so-called "multibag" in which bags are connected to each other by tubes is used for blood component transfusion or preparing blood preparations. In such a blood bag system, blood stored in a blood collection bag (main bag) is separated into a plasma component layer at the upper layer and a blood cell component layer at the lower layer by centrifugation. The separated plasma component should be taken out without mixing with the blood cell component. For this purpose, there are known liquid separators, for example, disclosed in JP-B-57-30507 and JP-B-63-47471. As shown in Fig. 7, the liquid separator 80 disclosed in JP-B-57-30507 comprises a box base 81 a wall plate 82 perpendicularly mounted on the box base 81, a separator plate 83 pivotally supported on the box base 81 and movable toward the wall plate 82, a lever 84 for pushing the separator plate 83, and a hook 85 for the lever 84. The wall plate 82 is provided with a hanger 86 for hanging a blood bag. A blood bag after centrifugation is hung by the hanger 86 of the wall plate 82 and the lever 84 is then moved upward to sandwich the blood bag between the separator plate 83 and the wall plate 82. The blood bag is pressed by the separator plate 83 and the wall plate 82 so that the plasma component of the upper layer of blood in the blood bag is discharged through a tube connected to the blood bag. As shown in Fig. 8, the liquid separator 90 disclosed in JP-B-63-47471 comprises a side wall 91 of a box case 92, connecting rods 94 and 95 and a pressing plate 93 arranged parallelly with the side wall 91. The pressing plate 93 can be moved toward the side wall 91 by the connecting rods 94 and 95. A blood bag 96 after centrifugation is sandwiched between the side wall 91 and the pressing plate 93 and pressed by the pressing plate 93 so that blood in the blood bag 96 is discharged. The plasma component separated from blood cell component in a blood bag should be taken out from the blood bag without mixing with the blood cell component and with good efficiency. In the liquid separator 80 disclosed in JP-B-57-30507, the blood bag is pressed by manipulating the lever 84. However, a delicate manipulation of the lever 84 is required in order not to disturb the boundary between the plasma component and the blood cell component in the blood bag. Such a delicate manipulation was hard. In the liquid separator 90 disclosed in JP-B-63-47471, the blood bag 96 is automatically pressed. The pressure for the blood bag 96 is fixed or increased at the end of the pressurization. In this liquid separator 90, however, there is a high possibility that the boundary between the plasma component and the blood cell component in the blood bag is disturbed and both are mixed with each other. Mixing of the components obstructs the accurate operation of a sensor for detecting the boundary between the components. DE-A-2 136 242 discloses a liquid separator for transfusion of blood or separating blood components from each other. The liquid separator comprises two plates hingedly connected for pressing a liquid container therebetween. A shaft member including a spring member is connected to a pushing member, which pushes the plates together for discharging liquid from the flexible container. Accordingly, it is an object of the present invention to provide a method of separating liquid into an upper liquid layer (for example, blood plasma component) and a lower liquid layer (for example, blood cell component) in a blood bag or the like in such a manner that the upper layer can be automatically discharged from the blood bag or the like without disturbing the boundary between the upper and lower liquid layers and mixing the upper liquid layer with the lower liquid layer and without any complicated and troublesome manipulation. As claimed, a method is provided using a flexible liquid container including liquid separated into an upper liquid layer and a lower liquid layer, which method implies the use of a liquid separator comprising a first and a second plate member between which plate members a receiving portion is formed for receiving the flexible liquid container. Pushing means are provided for pushing the second plate member toward the first plate member, the pushing means comprising a pushing member, and further drive means is provided for driving the pushing member toward the second plate member. Still further, a spring member is disposed between the pushing member and the second plate member, the second plate member being pushed through the spring member. A shaft member is arranged coaxially with the spring member and movably penetrating the pushing member. According to the invention the drive means of the pushing means stops driving the pushing member after the second plate member is pushed at least till the discharge of the upper liquid layer from the flexible liquid container starts. Subsequently, the second plate member is pushed by the restoring force of the spring member compressed between the pushing member and the second plate member so that the second plate member is pushed with gradually decreasing pressure. The invention is further elucidated by the following description of preferred embodiments thereof and the drawings. In the drawings: Fig. 1 is a schematic cross sectional view of a liquid separator used according to the present invention; Fig. 2 is a cross section taken along line I-I of Fig. 1; Figs. 3(a) through 3(c) are views illustrating the operation of the liquid separator of the present invention: Fig .4 is a perspective view of an embodiment in which a liquid separator used according to the present invention is applied to an automatic blood separator; Fig. 5 is a front elevation of the blood separator of Fig .4 in which quadruple blood bag is set; Fig.6 is a view of the quadruple blood bag of Fig.5; Figs. 7 and 8 are views of prior art liquid separators; and Figs. 9 are views illustrating the operation of the prior art liquid separator of Fig. 7. DETAILED DESCRIPTION The method according to the present invention will be described with reference to embodiments of liquid separators shown in the drawings. The liquid separator 1 used according to the present invention comprises a first plate member 2, a second plate member 3 forming a receiving portion 9 between it and the first plate member 2 for receiving a flexible liquid container 8 including liquid separated into the upper liquid layer and the lower liquid layer, and pushing means for pushing the second plate member 3 toward the first plate member 2, said pushing means automatically pushing the second plate member 3 with gradually decreasing pressure after starting the discharge of the upper liquid layer from the flexible liquid container 8. An embodiment in which the liquid separator 1 used according to the present invention is applied to a blood separator will be described with reference to Figs.1 through 3. Fig. 1 is a schematic cross sectional view of the liquid separator 1. Fig. 2 is a cross section taken along line I-I of Fig.1. Figs. 3(a) through 3(c) are views illustrating the operation of the liquid separator 1. The liquid separator 1 comprises a first plate member 2, a second plate member 3 forming a receiving portion 9 between it and the first plate member 2 for receiving a flexible liquid container 8 including liquid separated into the upper liquid layer and the lower liquid layer, and pushing means for pushing the second plate member 3 toward the first plate member 2. The pushing means comprises a pushing member 4, a spring member 5 disposed between the pushing member 4 and the second plate member 3, a shaft member 7 inserted in the spring member 5 and movably penetrating the pushing member 4, and drive means 6 for driving the pushing member 4 toward the second plate member 3. The second plate member 3 is pushed through the spring member 5. The first plate member 2 is pivotally supported at its bottom portion. It is rotatable from a position shown by broken lines in Fig.3(a) to a position shown by solid lines. It is fixed at the position shown by the solid lines after the liquid container 8 is received in the receiving portion 9. The second plate member 3 is pivotally supported at its upper end portion. It is rotatable toward the first plate member 2. Although the first and second plate members 2 and 3 are preferably flat, they may be curved moderately. The drive means 6 comprises an electric motor 16 and transmitting means 14 for transmitting the torque of the motor 16 to a rotational shaft 12. The rotational shaft 12 is rotated to move the pushing member 4 toward the second plate member 3 as shown in Fig.2 and Figs.3(a) through 3(c). The pushing member 4 is movably penetrated by the shaft member 7. The shaft member 7 extending between the pushing member 4 and the second plate member 3 is provided with the spring member 5. In this arrangement, when the pushing member 4 is moved toward the second plate member 3, it pushes the rear end of the spring member 5. The front end of the spring member 5 then pushes the second plate member 3 and the spring member 5 is compressed between the pushing member 4 and the second plate member 3. The shaft member 7 preferably advances in accordance with the compression of the spring member 5. For this purpose, the spring member 5 is wound on the shaft member 7 without looseness. If the spring member 5 is not curved, the shaft member 7 may not be disposed. The liquid container 8 compressed by the first and second plate members 2 and 3 is, for example, a blood bag provided with a tube 10 at its upper end. Blood in the blood bag has been separated into the plasma component at the upper liquid layer and the blood cell component at the lower liquid layer by centrifugation. The operation of the liquid separator 1 will be described with reference to Figs.3(a) through 3(c). Fig.3(a) shows the state in which the centrifuged blood bag is attached to the liquid separator 1. The drive means 6 is then operated to move the pushing member 4 toward the second plate member 3 as shown in Fig.3(b). The spring member 5 then pushes the second plate member 3 and is compressed as shown in Fig.3(b). The drive means 6 is stopped when the pushing member 4 reaches a predetermined position. The predetermined position varies in accordance with the volume of the used liquid container 8 (200 ml or 400 ml). In any case, however, it has been determined such that liquid flows out from the liquid container 8 through the tube 10 due to the compression by the first and second plate members 2 and 3 when the pushing member 4 is at the predetermined position. More specifically, it is generally determined to the position at which about 90% of the upper liquid layer (if the percentage of the upper liquid layer is 50% of the whole amount of the liquid, it is about 45% of the whole amount of the liquid) has flowed out from the liquid container 8. Fig.3(b) shows the state in which the drive means 6 is stopped. The spring member 5 which has been compressed by the pushing member 4 and the second plate member 3 pushes the second plate member 3 by its restoring force as shown in Fig.3(c). Because the restoring force gradually decreases, it is possible to discharge the upper liquid layer from the liquid container 8 through the tube 10 without disturbing the boundary between the upper and lower liquid layers in the liquid container 8. By using the Spring member 5 for pushing the second plate member 3, the pushing force gradually decreases after the upper liquid layer starts to flow out of the liquid container 8. Therefore, the upper liquid layer can be discharged from the liquid container 8 through the tube 10 without disturbing the boundary between the upper and lower liquid layers in the liquid container 8. The second and first plate members 3 and 2 are provided with liquid detecting means 11a and 11b for detecting the lower liquid layer. On the basis of the detection of the lower liquid layer (the boundary between the upper and lower liquid layers) by the detecting means 11a and 11b, closing means (not shown) is operated to close the tube 10, completing the liquid separation operation. The detecting means 11a and 11b may consist of an optical sensor comprising a light emitting element and a light receiving element or an ultrasonic sensor comprising a transmitting element and a receiving element. The drive means for driving the pushing member 4 is not limited to the electric motor as described above but it may consist of an air cylinder or a hydraulic cylinder. In the liquid separator there is used automatic drive means described above. Therefore, any complicated and troublesome manipulation is not required and the upper liquid layer in the liquid container can be easily taken out. In the liquid separator 1 of this embodiment, when the first plate member 2 is at the position shown by the solid lines, the second plate member 3 is at the position at which the upper end of the second plate member 3 is near the upper end of the first plate member 2 as shown in Fig.1 and Figs.3(a) through 3(c). The second plate member 3 is pivotally supported at its upper end portion and rotatable toward the first plate member 2. Therefore, the liquid container 8 is compressed by the rotation of the second plate member 3 from the upper portion of the liquid container 8 to the lower portion thereof. As the second plate member 3 is rotated, the space provided between the upper parts of the first and second plate members 2 and 3 is decreased as shown in Fig.3(c). Accordingly, the amount of the upper liquid layer remaining in the liquid container 8 becomes little. In contrast to this, in the prior art liquid separator 80 shown in Fig.9, the liquid container 8 is compressed from the lower portion to the upper portion as shown in Figs.9. Thus, when rotating the separator plate 83, the upper portion of the liquid container 8 has a portion B which never comes into contact with the wall plate 82. Accordingly, the boundary between the upper and lower liquid layers in the liquid container 8 can be detected only at a level A lower than the portion B. Thus, because the boundary can not be detected at a level near the upper end of the liquid container 8 the efficiency of taking out the upper liquid layer is bad. Besides, in this prior art liquid separator 80, when the liquid container 8 is compressed by the wall plate 82 and the separator plate 83, the upper portion of the liquid container 8 is expanded. Therefore, the amount of the upper liquid layer remaining in the liquid container 8 becomes much, lowering the efficiency of taking out the upper liquid layer. Furthermore, in this prior art liquid separator 80, because the liquid container 8 is compressed from the lower portion to the upper portion, there is the possibility that the liquid container 8 is lifted up when advancing the compression. Thus, it is difficult to set the level of an automatic boundary detection. In contrast to this, in the liquid separator 1 of this embodiment, the whole of the upper portion of the liquid container 8 comes into close contact with the first and second plate members 2 and 3. Therefore, in the upper end portion of the liquid container 8, there is formed no portion which does not come into contact with the second plate member 3. Accordingly, it becomes possible to detect the boundary between the upper and lower liquid layers in the liquid container 8 at a higher level. Further, when the liquid container 8 is compressed by the first and second plate members 2 and 3, the upper portion of the liquid container 8 becomes flat. Thus, the amount of the upper liquid layer remaining in the liquid container 8 is little, resulting in a good efficiency of taking out the other liquid layer. Furthermore, because there is no possibility that the liquid container 8 is lifted up because the liquid container 8 comes into close contact with the first and second plate members 2 and 3, it is easy to set the level of an automatic boundary detection. The liquid container 8 is, for example, a blood bag which contains an anticoagulant liquid for collecting blood. Specifically, the liquid container 8 is made of a flexible synthetic resin into a bag. The liquid container 8 is provided with a tube 10 which is in fluid communication with the interior of the liquid container 8. The tube 10 is made of a flexible synthetic resin such as flexible vinyl chloride and silicone resin like the liquid container 8. In this blood bag system, a plasma component container is connected to the other end of the tube 10. The tube 10 is provided with breakable communicating means for preventing the anticoagulant liquid in the blood bag from flowing into the plasma component container prior to blood collection. Example Next, an example of an automatic liquid separator used according to the present invention will be described. Fig. 4 is a perspective view of an automatic blood separator 30. Fig.5 is a front elevation in which a blood bag system is attached to the blood separator 30 of Fig. 4 and the first plate member 2 is set up and fixed. The blood separator 30 can employ any type of blood bags of 200 ml and 400 ml. The blood separator 30 can also employ any of double blood bag, triple blood bag and quadruple blood bag. In this example, quadruple blood bag (400 ml) shown in Fig. 6 is employed. The quadruple blood bag comprises a main bag as the flexible liquid container 8, a first transfer bag 51, a second transfer bag 52 and a third transfer bag 53. The first to third transfer bags 51 to 53 are flexible bags like the main bag 8. A tube 10 is connected to the main bag 8. The tube 10 is provided with breakable communicating means 56. Holes 55 are formed in the upper portion of the main bag 8. The first transfer bag 51 is in fluid communication with the tube 10 through a branched tube 60 and a tube 62. Similarly, the second transfer bag 52 is in fluid communication with the tube 10 through the branched tube 60, a tube 63, a branched tube 61 and a tube 64. Further, the third transfer bag 53 is in fluid communication with the tube 10 through the branched tube 60, the tube 63, the branched tube 61 and a tube 65. All tubes are made of flexible synthetic resin. A slit 57 is formed in each of the second and third transfer bags 52 and 53. After collecting blood in the main bag 8, a tube 66 used for the blood collection is closed and cut off. The quadruple blood bag has been centrifuged to separate blood in the main bag 8 into the upper liquid layer of plasma component, the intermediate layer of buffy coat layer including platelet and white blood cells, and the lower liquid layer of blood cell component. The blood separator 30 comprises a housing 31 and a cover 35. The first plate member 2 is attached to the front portion of the housing 31 so as to be able to be opened and closed. The second plate member 3 is attached in the housing 31 at the rear of the first plate member 2. Above the second plate member 3 are disposed hooks 37 to be inserted in the holes 55 of the flexible liquid container (main bag) 8. The first and second plate members 2 and 3 are provided with liquid detecting means 11a and 11b which are for detecting the boundary between the plasma layer and the buffy coat layer separated in the main bag 8 and the boundary between the buffy coat layer and the blood cell layer. The liquid detecting means 11a and 11b consist of, for example, a photosensor which detects the boundaries on the basis of the difference in absorbance, transmittance or reflectivity between the layers. A power switch 40 is disposed on the lower left side of the front surface of the housing 31. Control panels 41 and 42 including various control switches are disposed in the front surface of the housing 31. A main bag receiving portion 36 is formed between the first and second plate members 2 and 3. The first plate member 2 is open in Fig. 4 and the main bag 8 is put in the receiving portion 36 in this state and then the first plate member 2 is closed as shown in Fig.5. In the housing 31 is disposed pushing means for pushing the second plate member 3 with gradually decreasing pressure after starting the discharge of the upper liquid layer from the main bag 8 as shown in Fig.1. A receiving portion 32 for the first transfer bag 51 is formed in the upper surface of the housing 31 as shown in Figs.1 and 4. On the upper surface of the housing 31 are disposed a first tube clamper 43 for opening and closing the tube 10, a second tube clamper 44 for opening and closing the tube 62, a third tube clamper 45 for opening and closing the tube 64, and a fourth tube clamper 46 for opening and closing the tube 65 as shown in Figs.1, 4 and 6. Each tube clamper is driven by a solenoid connected to the tube clamper. A weight sensor 38 is disposed in a tray forming the receiving portion 32 as shown in Fig. 1. As shown in Fig.5, hooks 33 and 34 are disposed on the cover 35. The second transfer bag 52 is hung by the hook 33 through the slit 57 formed in the bottom portion of the second transfer bag 52 and the third transfer bag 53 is hung by the hook 34 through the slit 57 formed in the bottom portion of the third transfer bag 53. After setting each blood bag as shown in Fig.5, the first plate member 2 is closed. The communicating means 56 is then broken. When a separation start switch is turned on, the tube clampers 43 and 45 are open and the tube clampers 44 and 46 are closed. The drive means then starts and the second plate member 3 is moved toward the first plate member 2. Then the upper liquid layer of plasma component flows from the main bag 8 into the second transfer bag 52 hung by the hook 33 through the tubes 10, 63 and 64. When the liquid detecting means 11a and 11b detect the boundary of the red blood cell component, the tube clampers 43 and 45 are closed. Subsequently, the tube clampers 43 and 44 are opened. Then the plasma component, the pia mater layer and the red blood cell component remaining in the main bag 8 flows in the first transfer bag 51 in this order through the tubes 10 and 62. When the weight sensor 38 disposed in the tray 32 receiving the first transfer bag 51 detects that the weight of the first transfer bag 51 reaches a first predetermined value, the tube clampers 43 and 44 are closed. Then the second plate member 3 is released from pushing and the first plate member 2 is opened. Subsequently, the tube clampers 44 and 45 are opened so that the plasma flows from the second transfer bag 52 into the first transfer bag 51. When the weight sensor 38 of the tray 32 detects that the weight of the first transfer bag 51 reaches a second predetermined value, the tube clampers 44 and 45 are closed. In a liquid separator used according to the present invention, wherein, the pushing means automatically pushes the second plate member with gradually decreasing pressure after starting the discharge of the upper liquid layer from the flexible liquid container, The upper liquid layer can be discharged from the flexible liquid container without disturbing the boundary between the upper and lower liquid layers in the flexible liquid container. Thus, the upper liquid layer can automatically and efficiently be taken out from the flexible liquid container without mixing with the lower liquid layer and without any complicated and troublesome manipulation. If the discharge of the upper liquid layer is automatically stopped with a sensor detecting the boundary between the upper and lower liquid layers, it is possible to decrease errors of the sensor caused by the disturbance of the boundary.

Claims: A method of separating liquid in a flexible liquid container (8) including liquid separated into an upper liquid layer and a lower liquid layer, the method implying use of a liquid separator comprising a first and a second plate member (2, 3), wherein a receiving portion (9) is formed between the first and the second plate members (2, 3) for receiving the flexible liquid container (8), and pushing means (4 to 7) for pushing the second plate member (3) toward the first plate member (2), the pushing means comprising a pushing member (4) and drive means (6) for driving the pushing member (4) toward the second plate member (3), a spring member (5) disposed between the pushing member (4) and the second plate member (3), the second plate member (3) being pushed through the spring member (5), and a shaft member (7) arranged coaxially with the spring member (5) and movably penetrating the pushing member (4), characterised in that the drive means (6) of the pushing means (4 to 7) stops driving the pushing member (4) after the second plate member (3) is pushed at least till the discharge of the upper liquid layer from the flexible liquid container (8) starts, and subsequently, the second plate member (3) is pushed by the restoring force of the spring member (5) compressed between the pushing member (4) and the second plate member (3) so that the second plate member (3) is pushed with gradually decreasing pressure. The method of claim 1, wherein the lower liquid layer in the liquid container (8) or the boundary between the upper and lower liquid layers in the liquid container (5) disposed in the upper portion of the receiving portion (9) for the liquid container are detected. The method of claim 1 or 2, wherein the distance between the upper end portions of the first and second plate members (2, 3) is kept constant when the liquid container (8) is compressed and the second plate member (3) is pivotally supported at its upper end portion and is rotated toward the first plate member (2) to compress the liquid container (8) from the upper portion to the lower portion.

Inventors: FURUYA AKIHIKO, INABA FUMIAKI C O TERUMO KABUS, KOBAYASHI SUSUMU, TANOKURA NOBUKAZU C O TERUMO K, FURUYA, AKIHIKO, INABA, FUMIAKI, C/O TERUMO KABUSHIKI KAISHA, KOBAYASHI, SUSUMU, TANOKURA, NOBUKAZU, C/O TERUMO KABUSHIKI KAISHA
Applicants: TERUMO CORP, TERUMO KABUSHIKI KAISHA
Application year: 1990
Main classification: A61M1
IPC codes: B04B11, B01D17, A61M1