Patent ID: 7503905

Claim:
In a syringe-to-syringe mixing system that includes a first syringe loaded with a first component and a second syringe loaded with a second component, and wherein the two syringes are coupleable so that the barrel of the first is in fluid communication with the barrel of the second so as to permit mixing of the first and second components as the contents of one syringe barrel is injected into the other, at least one of the syringes comprising an improved vented plunger assembly situated within one of the syringe barrels of the syringe-to-syringe mixing system, the plunger assembly comprising: a hollow outer sleeve which fits within the barrel of one of the syringes, the sleeve having an interior surface and means for sealing the hollow outer sleeve against an inner surface of the syringe plunger; an inner stem disposed within the hollow outer sleeve so that the hollow outer sleeve and inner stem are operable to be alternately pushed together into the syringe barrel and withdrawn together from the barrel when used as a plunger assembly for performing a back and forth mixing action between syringe barrels of the first and second syringes, the inner stem having an exterior surface, the inner stem being movably disposed within the outer sleeve between open and closed positions; a venting passageway being defined between the exterior surface of the inner stem and the interior surface of the hollow outer sleeve; and means for selectively moving the inner stem within the outer sleeve to either the open or closed positions and then temporarily locking the inner stem in the selected position, so that the venting passageway will remain in the selected open or closed position irrespective of whether the plunger assembly is thereafter pushed into our pulled out of the syringe barrel in which the plunger assembly is used.