Patent ID: 7267668

Claim:
A syringe comprising: a) a hollow barrel comprising a first barrel end and a second barrel end, said first barrel end being open and said second barrel end comprising means for allowing attachment of a needle assembly, said barrel having a first chamber and a second chamber of substantially equal diameters; b) said first chamber accommodating a non-therapeutic compressible gas which is not to be dispensed out of said first chamber; c) said second chamber accommodating a therapeutic fluid capable of being dispensed out of said second chamber; d) a master plunger assembly mounted in said barrel for longitudinal movement therein, said master plunger assembly comprising a master plunger having a diameter located in said first chamber and a plunger member extending through said first barrel end for allowing a user to apply pressure thereto; e) a single slave plunger having a diameter substantially equal to the diameter of said master plunger located in said second chamber of said barrel between said master plunger assembly and said second barrel end for longitudinal movement therein and to define a single therapeutic fluid chamber extending longitudinally from said slave plunger to said second barrel end, and to define a single pneumatic chamber containing said non-therapeutic compressible gas extending longitudinally from said slave plunger to said master plunger assembly, said slave plunger further serving to both isolate the therapeutic fluid and non-therapeutic compressible gas from each other and further serve to prevent the non-therapeutic compressible gas from being dispensed out of the syringe; wherein only two plungers are within said barrel, and fluid cannot transfer through either of the two plungers; and wherein, when said therapeutic fluid chamber contains a therapeutic fluid to be dispensed from said syringe, a user applying selective pressure to said plunger member will cause said master plunger assembly to slide towards said slave plunger and compress said non-therapeutic compressible gas against said slave plunger, said slave plunger will as a result of said pressure slide towards said second barrel end as said gas decompresses and apply pressure against said therapeutic fluid as a result thereof, and said therapeutic fluid will be dispensed out of the syringe via the means for allowing attachment of a needle assembly, wherein said slave plunger is effective to prevent escape of said non-therapeutic compressible gas as the therapeutic fluid is dispensed out of the syringe via said second barrel end in accordance with said pressure applied to the plunger member.