Dual resolution syringe

A syringe for metering and dispensing incrementally different volumes of fluid comprising:

• a plunger with an elongated passage extending therethrough:
• a housing concentric with and movable relative to the plunger and at least in part defining a fluid receiving chamber at one end of the plunger;
• a piston positioned and longitudinally movable in and relative to the housing, the piston shaped and sized to occupy selected volumes of the chamber and having an outer surface at least in part spaced from the inner surface of the housing;
• and
• sealing means forming an end of the chamber remote from the one end of the plunger, said means fixed to the inner surface of the housing and movable relative to the piston, whereby movement of the piston toward the plunger initially reduces the volume of the chamber by a first volume equal to the change in the volume of the piston positioned between the sealing means and the plunger, and thereafter a second volume by relative movement of the sealing means and piston;
• and
• further comprising a second sealing means for the chamber, said second sealing means fixed to the plunger, positioned between the plunger and the inner surface of the housing, and defining an end of the chamber proximal the plunger.

A syringe for metering sequential different volumes of fluid contained in the syringe including:

• a housing;
• a piston within the housing;
• and
• a plunger extending from the housing;
• a chamber formed in the housing between the plunger and a sealing means between the piston and the inner surface of the housing;
• the piston having a volume less than the volume of that portion of the chamber that is coextensive with the portion of the piston in the chamber;
• the plunger having an elongated passageway extending therethrough:
• means for aspirating a first volume of said fluid by movement of the sealing means relative to the piston, and thereafter a second lesser volume of fluid by further movement of the sealing means relative to the piston;
• and
• means for ejecting the second volume of fluid through the elongated passage in the plunger by movement of the piston relative to the plunger.