Patent ID: 7160265

Claim:
A needle-less injection device, comprising (a) a cannula ( 5 ) insertable in a housing ( 3 ), and fillable with a predetermined active substance ( 11 ) for injection, and comprises a piston ( 9 ) movable in a cannula housing for ejecting the active substance ( 11 ) from an outlet opening ( 53 ) in the cannula housing, (b) a propellant charge cartridge ( 7 ) insertable into the housing ( 3 ) and comprising a housing containing a propellant charge ( 19 ) and a device ( 23 ) for igniting the propellant charge ( 19 ), (c) a propelling surface ( 15 ) movable in a part ( 3 a ) of the housing of the injection device ( 1 ) or in the housing of the cannula ( 5 ) or in the cartridge housing and movable by the gas pressure generated after ignition of the propellant charge ( 19 ), out of a starting position into an end position, the outer periphery of the propelling surface being sealed from the inner periphery of each housing during the entire displacement, wherein the propelling surface ( 15 ) acts upon the piston ( 9 ) movable in the cannula housing, and (d) wherein the propelling surface ( 15 ), in the outer region of its end face acted upon by the gas pressure, has an annular recess such that when pressurized by the gas, a lid-like wall ( 63 ) between the annular recess and the outer periphery of the propelling surface ( 15 ) is pressed, with preferably elastic deformation, against the inner wall of the respective housing, so as to have a sealing effect.