US Patent 7789862 Multi-chamber, sequentially dispensing syringe

A discharge assembly is disclosed which partitions a conventional syringe into proximal and distal chambers to provide a multi-chamber, sequentially dispensing syringe apparatus. Incorporated in the discharge assembly is a syringe stopper body and an associated valve stem which in combination form a valve. A syringe plunger communicates through fluid in the proximal chamber to force displacement of the discharge assembly. The valve is actuated by collision between a rigid member which is a part of the valve stem and the distal internal surface of the syringe. The discharge assembly may be made from two parts: (1) the stopper body (made from conventional syringe stopper material); (2) the valve (actuating) stem made from rigid material similar to material from which the syringe barrel is made. Key features of such a multi-chamber syringe apparatus are (1) fluids in the chambers are kept disparate; (2) the discharge assembly may be used in conventional syringes; (3) gas in a closed chamber, proximal to the discharge assembly, is retained in the proximal chamber while only liquid is dispensed therefrom.