Patent ID: 8221347

Claim:
In a needle-free injection device for delivering a medicament under pressure from a dosing reservoir through an outlet orifice for administration to an animal or human, of the type comprising a plunger slidably received in said dosing reservoir and movable in a forward direction for expelling said medicament through said orifice, the improvement comprising an actuating device, said actuating device comprising: (a) a gas tight chamber; (b) a piston and rod assembly slidably received in said chamber and movable between a forward position and a rearward position; (c) a gas charge in said chamber for urging said piston and rod assembly to said forward position; (d) means for moving said piston and rod assembly against said gas charge into said rearward position; and (e) a trigger for releasably retaining said piston and assembly in said rearward position wherein said trigger comprises a triggering lever having a first end and a second end and being pivotable about a pivot member and connected at said first end to a push rod, whereby when a downward force is exerted on said second end of said triggering lever it pivots about said pivot member and said first end is raised causing said push rod to disengage said actuating member such that said piston and rod assembly moves from said rearward position to said forward position, whereby activating said trigger causes said piston and rod assembly to be released for movement by said gas charge to said forward position so as to impact said plunger directly or indirectly with a force sufficient to cause said plunger to move in said forward direction to expel said medicament through said outlet and whereby said gas tight chamber is adapted to minimize or prevent the escape of said gas charge so as to maintain said gas charge in a pressurized state.