Serum/plasma separator assembly having interface-seeking piston

Claim 1

A SEPARATOR ASSEMBLY CAPABLE OF SEPARATING BLOOD INTO A PLASMA/SERUM OR LIGHT PHASE AND A CELLULAR OR HEAVY PHASE COMPRISING A CONTAINER HAVING AT LEAST ONE OPEN END WHICH IS ADAPTED TO RECEIVE BLOOD FOR SUBSEQUENT SEPARATION INTO A LIGHT PHASE AND A HEAVY PHASE, A CLOSURE SEALING THE OPEN END OF THE CONTAINER, THE CLOSURE BEING FORMED OF A SELF-SEALING, ELASTOMERIC MATERIAL WHICH IS PENETRABLE BY A CANNULA THROUGH WHICH BLOOD TO BE SEPARATED IS CONDUCTED INTO THE CONTAINER, AN INTERFACE-SEEKING PISTON HAVING A SPECIFIC GRAVITY GREATER THAN BLOOD AND SLIDABLY MOUNTED IN THE CONTAINER ADJACENT ONE END THEREOF AND ADAPTED TO MOVE DOWNWARDLY IN SAID CONTAINER UNDER THE INFLUENCE OF CENTRIFUGAL FORCE, SAID PISTON HAVING AT LEAST TWO SPACED SEALING RINGS ON AN OUTER SURFACE IN SEALING ENGAGEMENT WITH THE INNER SURFACE OF THE CONTAINER, SAID PISTON HAVING A PASSAGE FOR CONDUCTING SEPARATED SERUM/PLASMA, ONE OF SAID SEAL RINGS BEING DEFORMABLE TO PROVIDE AN OPENING TO CONNECT SAID PASSAGE WITH THE CONTAINER BELOW THE PISTON, COARSE FILTER MEANS MOUNTED ON SAID PISTON AND BEING IN FLUID COMMUNICATION WITTH SAID PASSAGE SO THAT ALL THE SEPARATED PLASMA/SERUM IS FILTERED AS THE PISTON MOVES DOWNWARDLY IN THE CONTAINER, SAID COARSE FILTER HAVING PORE SIZES LARGE ENOUGH TO PASS THE CELLULAR PHASE OF THE BLOOD BUT SMALL ENOUGH TO REMOVE FIBRIN STRANDS, AND FINE FILTER MEANS HAVING A PORE SIZE SMALLER THAN SAID CELLULAR PHASE, MOUNTED ON SAID PISTON SO AS TO RECEIVE THE PLASMA/SERUM FILTERED BY THE COARSE FILTER MEANS WHEREBY WHEN THE PISTON REACHES SAID INTERFACE IT WILL AUTOMATICALLY STOP.