Apparatus and method for separation of blood

An apparatus for the separation of the liquid phase from the cellular phase of a blood sample comprising:

• a blood collection tube open at one end and closed at the other end for collecting a sample of blood and for holding the blood while it is separated into liquid and cellular phases;
• a separating tube open at both ends for receiving the separated liquid phase of smaller diameter than the collection tube so that it can be telescopically shifted therein;
• a piston assembly for use in separating the liquid phase from the cellular phase comprising an inverted cup shaped body portion disposed in the end of the separating tube which is inserted in the collection tube in sealing engagement with the interior walls thereof and formed with a one-way valve extending through the inner portion thereof and with a peripheral flexible sealing flange extending around the outer portion thereof and projecting outwardly beyond the wall of the separator tube;
• said flange being of greater diameter than the internal diameter of the collection tube and having a smooth lower surface so as to have wiping engagement with the inner walls of said collection tube when the piston assembly is shifted inwardly in the collection tube, and having a radially grooved upper surface so as to provide air channels between said flange and the inner walls of the collection tube when the piston assembly is shifted outwardly from said collection tube;
• said valve being arranged to open when the separator tube and piston assembly are shifted inwardly through the liquid phase in the collection tube and to close when the shifting stops;
• and
• a filter disposed in said cup shaped housing and encased and protected thereby and arranged in engagement with the wall thereof so that liquid passing through said valve must pass through the filter.